Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

While the short-term relationship between clouds and aerosols is well known, no adequate data is available to verify the longer-term, annual to decadal, relationship. It is important to quantify the aerosol–cloud interaction (ACI) for mitigating uncertainty in climate prediction. Here the long-term ACI over the mid-to-high latitudes of the Northern Hemisphere was analyzed by using seasonally-resolved ion fluxes reconstructed from a southeastern Greenland ice core (SE-Dome ice core) as aerosol proxies, and satellite-based summer cloud amount between 1982 and 2014. As a result, SO₄²⁻ flux in the ice core shows significant positive correlation with total cloud amounts ($${CC}_{T}$$) and cloud droplet concentration ($${N}_{d}$$) in the summer over the southeastern Greenland Sea, implying that the sulfate aerosols may contribute to the variability of $${CC}_{T}$$ via microphysical cloud processes. Significant positive correlations are persistent even under the constrained conditions when cloud formation factors such as relative humidity, air temperature at cloud height, and summer North Atlantic Oscillation are limited within ± 1σ variability. Hence sulfate aerosols should control the interannual variability of summer $${CC}_{T}$$ In terms of decadal changes, $${CC}_{T}$$ was approximately 3–5% higher in the 1960s–1970s than in the 1990s–2000s, which can be explained by changes in the, $${ { {\text{SO } } }_{4 } }^{2-}$$ flux preserved in the SE-Dome ice core.

DOI： 10.1038/s41598-024-59817-7

Web of Science

PubMed

Other Link： https://www.nature.com/articles/s41598-024-59817-7

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Accurately quantifying runoff sources and understanding hydrological processes in glaciated mountain basins is essential for effective water resource management in the face of climate change. This study aimed to determine the contributions from various runoff sources in glaciated basins within the inner Tien-Shan mountains of Kyrgyzstan by utilizing integrated land surface, glacier energy-mass balance, and river routing models. To account for local topographic influences on solar radiation and cloud transmissivity processes, gridded meteorological forcing data were downscaled. The integrated models were then evaluated against observed discharge, glacier mass balance, and snow water equivalent, with a focus on the Kara-Batkak glacier reference site. Shortwave radiation correction was particularly important for improving the accuracy of model simulations. The results indicate that the peak glacier melt contribution occurs in July and August, with some basins reaching up to 54%. On an annual basis, the average contribution from glaciers across the basins was found to be 19%, while the ratios of snowmelt and rainfall were 58% and 23%, respectively. This study highlights the utility of integrated modelling approaches in understanding and quantifying runoff components in data-scarce high mountain regions. The incorporation of observed glacier data proved to be crucial for accurately representing hydrological processes under current climatic conditions. These findings underscore the significance of considering glacier dynamics and their influence on water resources to inform effective water management strategies in glaciated mountain basins.

DOI： 10.3389/feart.2023.1306476

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Abstract

Tropospheric reactive bromine (Br_y) influences the oxidation capacity of the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol acidity plays a crucial role in Br_y abundances through acid‐catalyzed debromination from sea‐salt‐aerosol, the largest global source. Bromine concentrations in a Russian Arctic ice‐core, Akademii Nauk, show a 3.5‐fold increase from pre‐industrial (PI) to the 1970s (peak acidity, PA), and decreased by half to 1999 (present day, PD). Ice‐core acidity mirrors this trend, showing robust correlation with bromine, especially after 1940 (r = 0.9). Model simulations considering anthropogenic emission changes alone show that atmospheric acidity is the main driver of Br_y changes, consistent with the observed relationship between acidity and bromine. The influence of atmospheric acidity on Br_y should be considered in interpretation of ice‐core bromine trends.

DOI： 10.1029/2023GL107733

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

DOI： 10.1017/jog.2023.106

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Snow and Ice  

DOI： 10.5331/bgr.24A02

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. In situ meteorological data are essential to better understand ongoing environmental changes in the Arctic. Here, we present a dataset of quality-controlled meteorological observations from two automatic weather stations in northwest Greenland from July 2012 to the end of August 2020. The stations were installed in the accumulation area on the Greenland Ice Sheet (SIGMA-A site, 1490 m a.s.l.) and near the equilibrium line of the Qaanaaq Ice Cap (SIGMA-B site, 944 m a.s.l.). We describe the two-step sequence of quality-controlling procedures that we used to create increasingly reliable datasets by masking erroneous data records. Those datasets are archived in the Arctic Data archive System (ADS) (SIGMA-A – https://doi.org/10.17592/001.2022041303, Nishimura et al., 2023f; SIGMA-B – https://doi.org/10.17592/001.2022041306, Nishimura et al., 2023c). We analyzed the resulting 2012–2020 time series of air temperature, surface height, and surface albedo and histograms of longwave radiation (a proxy of cloudiness). We found that surface height increased, and no significant albedo decline in summer was observed at the SIGMA-A site. In contrast, high air temperatures and frequent clear-sky conditions in the summers of 2015, 2019, and 2020 at the SIGMA-B site caused significant albedo and surface lowering. Therefore, it appears that these weather condition differences led to the apparent surface height decrease at the SIGMA-B site but not at the SIGMA-A site. We anticipate that this quality-controlling method and these datasets will aid in climate studies of northwest Greenland and will contribute to the advancement of broader polar climate studies.

DOI： 10.5194/essd-15-5207-2023

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Abstract

Snowpack emissions are recognized as an important source of gas‐phase reactive bromine in the Arctic and are necessary to explain ozone depletion events in spring caused by the catalytic destruction of ozone by halogen radicals. Quantifying bromine emissions from snowpack is essential for interpretation of ice‐core bromine. We present ice‐core bromine records since the pre‐industrial (1750 CE) from six Arctic locations and examine potential post‐depositional loss of snowpack bromine using a global chemical transport model. Trend analysis of the ice‐core records shows that only the high‐latitude coastal Akademii Nauk (AN) ice core from the Russian Arctic preserves significant trends since pre‐industrial times that are consistent with trends in sea ice extent and anthropogenic emissions from source regions. Model simulations suggest that recycling of reactive bromine on the snow skin layer (top 1 mm) results in 9–17% loss of deposited bromine across all six ice‐core locations. Reactive bromine production from below the snow skin layer and within the snow photic zone is potentially more important, but the magnitude of this source is uncertain. Model simulations suggest that the AN core is most likely to preserve an atmospheric signal compared to five Greenland ice cores due to its high latitude location combined with a relatively high snow accumulation rate. Understanding the sources and amount of photochemically reactive snow bromide in the snow photic zone throughout the sunlit period in the high Arctic is essential for interpreting ice‐core bromine, and warrants further lab studies and field observations at inland locations.

DOI： 10.1029/2023JD039257

Web of Science

Other Link： https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023JD039257

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Abstract

Arctic warming has accelerated surface melting even in the highland areas of the Greenland ice sheet (GrIS). Understanding the relationship between climate and surface melting is essential for improving the estimates of ice‐sheet mass loss due to warming. Here we analyze a 250 m‐long ice core from the southeastern dome of GrIS (SE‐Dome site; 67°19′17″ N, 36°47′03″ W, 3,161 m a.s.l.), where the annual mean temperature is −20.9°C and the accumulation rate is high and there is a large discrepancy among climate models regarding snow accumulation estimates. A time scale was established for 1799–2020 with a half‐year uncertainty using annual counting of H₂O₂ concentration and five time horizons determined by electrical conductivity, melt events, and tritium concentration. The annual accumulation rate from the ice core shows no significant trend over 221 years and has an average of 1.04 ± 0.20 m w.e. year⁻¹. In contrast, the frequency and thickness of refrozen melt layer (ML) have increased over 221 years, and are synchronized with temperature changes in the Arctic. The thickness of MLs correlates positively with the time‐integrated summer temperature anomaly using a reanalysis of air temperature. The in‐situ accumulation records in the southeastern GrIS provide an important basis for correcting reanalysis data such as ERA5, which in turn are valuable for improving regional climate models.

DOI： 10.1029/2023JD038874

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Abstract

High Mountain Asia (HMA) is among the most vulnerable water towers globally and yet future projections of water availability in and from its high‐mountain catchments remain uncertain, as their hydrologic response to ongoing environmental changes is complex. Mechanistic modeling approaches incorporating cryospheric, hydrological, and vegetation processes in high spatial, temporal, and physical detail have never been applied for high‐elevation catchments of HMA. We use a land surface model at high spatial and temporal resolution (100 m and hourly) to simulate the coupled dynamics of energy, water, and vegetation for the 350 km² Langtang catchment (Nepal). We compare our model outputs for one hydrological year against a large set of observations to gain insight into the partitioning of the water balance at the subseasonal scale and across elevation bands. During the simulated hydrological year, we find that evapotranspiration is a key component of the total water balance, as it causes about the equivalent of 20% of all the available precipitation or 154% of the water production from glacier melt in the basin to return directly to the atmosphere. The depletion of the cryospheric water budget is dominated by snow melt, but at high elevations is primarily dictated by snow and ice sublimation. Snow sublimation is the dominant vapor flux (49%) at the catchment scale, accounting for the equivalent of 11% of snowfall, 17% of snowmelt, and 75% of ice melt, respectively. We conclude that simulations should consider sublimation and other evaporative fluxes explicitly, as otherwise water balance estimates can be ill‐quantified.

DOI： 10.1029/2022WR033841

Web of Science

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablatingice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing theice surface albedo, accurate simulation of the temporal changes in CH depth is essential for understanding ice surface melt. We established a novelmodel that simulates the temporal changes in CH depth using heat budgets calculated independently at the ice surface and CH bottom based onhole-shaped geometry. We evaluated the model with in situ observations of the CH depths on the Qaanaaq ice cap in northwestern Greenland during the2012, 2014, and 2017 melt seasons. The model reproduced the observed depth changes and timing of CH collapse well. Although earlier models haveshown that CH depth tends to be deeper when downward shortwave radiation is intense, our sensitivity tests suggest that deeper CH tends to form whenthe diffuse component of downward shortwave radiation is dominant, whereas CHs tend to be shallower when the direct component is dominant. Inaddition, the total heat flux to the CH bottom is dominated by shortwave radiation transmitted through ice rather than that directly from theCH mouths when the CH is deeper than 0.01 m. Because the shortwave radiation transmitted through ice can reach the CH bottom regardless ofCH diameter, CH depth is unlikely to be correlated with CH diameter. The relationship is consistent with previous observationalstudies. Furthermore, the simulations highlighted that the difference in albedo between ice surface and CH bottom was a key factor for reproducingthe timing of CH collapse. It implies that lower ice surface albedo could induce CH collapse and thus cause further lowering of the albedo. Heatcomponent analysis suggests that CH depth is governed by the balance between the intensity of the diffuse component of downward shortwave radiationand the turbulent heat transfer. Therefore, these meteorological conditions may be important factors contributing to the recent surface darkening ofthe Greenland ice sheet and other glaciers via the redistribution of CHs.

DOI： 10.5194/tc-17-3309-2023

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

Abstract

Despite their importance for regional water resource planning and as indicators of climate change, records of in situ glacier mass balance remain short and spatially sparse in the Himalaya. Here, we present an updated series of in situ mass-balance measurements from Rikha Samba Glacier, Nepal, between 2011 and 2021. The updated in situ mass balance is −0.39 ± 0.32 m w.e. for this period. We use an energy-mass balance model to extend the annual mass-balance series back to 1974. The model is forced using daily meteorological variables from ERA5-Land reanalysis data that is linearly bias-corrected using observations from an automatic weather station situated near the glacier terminus. The modeled mass balance is consistent with the in situ mass-balance series measured 2011–2021 and with previous glaciological and geodetic estimates. The model results indicate a mass balance of −0.56 ± 0.27 m w.e. a⁻¹ over the reconstruction period of 1974–2021, which is comparable to the mass losses experienced by other Himalayan glaciers during this time. An assessment of the sensitivity of the glacier mass balance to meteorological forcing suggests that a change in temperature of ±1 K has a stronger effect on the calculated mass balance compared to a ±20% change in either precipitation, or relative humidity, or solar radiation.

DOI： 10.1017/jog.2022.93

DOI： 10.1017/jog.2022.93

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Other Link： https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143022000934

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Meteorological Society  

Abstract

The Asian Precipitation Experiment (AsiaPEX) was initiated in 2019 to understand terrestrial precipitation over diverse hydroclimatological conditions for improved predictions, disaster reduction, and sustainable development across Asia under the framework of the Global Hydroclimatology Panel (GHP)/Global Energy and Water Exchanges (GEWEX). AsiaPEX is the successor to GEWEX Asian Monsoon Experiment (GAME, 1995-2005) and Monsoon Asian Hydro-Atmosphere Scientific Research and Prediction Initiative (MAHASRI, 2006-2016). While retaining the key objectives of the aforementioned projects, the scientific targets of AsiaPEX focus on land-atmosphere coupling and improvements to the predictability of the Asian hydroclimatological system. AsiaPEX was designed for both fine-scale hydroclimatological processes occurring at the land surface and the integrated Asian hydroclimatological system characterized by multiscale interactions. We adopt six approaches including observation, process studies, scale interactions, high-resolution hydrological modeling, field campaigns, and climate projection, which bridge gaps in research activities conducted in different regions. Collaboration with mesoscale and global modeling researchers is one of the core methods in AsiaPEX. We review these strategies based on the literature and our initial outcomes. These include the estimation and validation of high-resolution satellite precipitation, investigations of extreme rainfall mechanisms, field campaigns over the Maritime Continent and Tibetan Plateau, areas of significant impact on the entire AsiaPEX region, process studies on diurnal to interdecadal scale interactions, and evaluation of the predictabilities of climate models for long-term variabilities. We will conduct integrated observational and modeling initiative, the Asian Monsoon Year (AMY)-II around 2025-2028, whose strategies are the sub-regional observation platforms and integrated global analysis.

DOI： 10.1175/BAMS-D-20-0220.1

DOI： 10.1175/bams-d-20-0220.1

Web of Science

Other Link： https://journals.ametsoc.org/downloadpdf/journals/bams/aop/BAMS-D-20-0220.1/BAMS-D-20-0220.1.xml

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

Abstract

We quantify the surface elevation changes along Yala Glacier in Langtang Valley, Nepal Himalaya, since 1981 using geodetic methods to understand the recent evolution and current state of small debris-free glaciers across the region. We analyse differential global positioning system measurements and aerial stereo imagery that were acquired along Yala Glacier in 2007, 2009, 2012 and 2015 to generate digital elevation models for each calculation period. Continuous surface lowering has mainly been observed across the down-glacier area during the calculation periods, although a large degree of variability exists, with this lowering trend propagating up-glacier in recent years. The area-weighted glacier mass balances range from −0.98 ± 0.27 to −0.26 ± 0.30 m w.e. a⁻¹ for the five calculation periods (1981–2007, 2007–2009, 2009–2012, 2012–2015 and 2007–2015). These calculated mass-balance data reveal that Yala Glacier has undergone accelerated mass loss since the late 2000s, which is consistent with the results of previous in situ measurement and remote-sensing studies.

DOI： 10.1017/jog.2022.118

DOI： 10.1017/jog.2022.118

Web of Science

Other Link： https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143022001186

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Meteorological Society  

Abstract

The processes underlying heavy rainfall in the higher elevations of the Himalayas are still not well-known despite its importance. Here, we examine the detailed process causing a heavy rainfall event, observed by our rain gauge network in the Rolwaling valley, eastern Nepal Himalayas, using ERA5 reanalysis and a regional cloud-resolving numerical simulation. Heavy precipitation (112 mm day⁻¹) was observed on July 8, 2019, at Dongang (2790 m above sea level). Most of the precipitation (81 mm) occurred during 19–23 local time (LT). The synoptic-scale environment is characterized by a monsoon low-pressure system (LPS) over northeastern India. The LPS lifted moisture upward from the lower troposphere and then horizontally transported it into the eastern Nepal Himalayas within the middle troposphere, increasing the content of the water vapor around Dongang. A mesoscale convective system passed over Dongang around the time of the intense precipitation. Numerical simulation showed surface heat fluxes prevailed under the middle tropospheric (~ 500hPa) southeasterly flow associated with the LPS around a mountain ridge on the upwind side of Dongang until 19 LT, enhancing convective instability. Topographic lifting led to the release of the enhanced instability, which triggered the development of a mesoscale precipitation system. The southeasterly flow pushed the precipitation system northward, which then passed over Dongang during 20–22 LT, resulting in heavy precipitation. Thus, we conclude that the heavy precipitation came from the multiscale processes such as three-dimensional moisture transport driven by the LPS and the diurnal variation in heat fluxes from the land surface.

DOI： 10.1175/JHM-D-22-0080.1

DOI： 10.1175/jhm-d-22-0080.1

Web of Science

Other Link： https://journals.ametsoc.org/downloadpdf/journals/hydr/aop/JHM-D-22-0080.1/JHM-D-22-0080.1.xml

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Recent studies of microbial biogeography have revealed the global distribution of cosmopolitans and dispersal of regional endemics, but little is known about how these processes are affected by microbial evolution. Here, we compared DNA sequences from snow/glacier algae found in an 8000-year-old ice from a glacier in central Asia with those from modern snow samples collected at 34 snow samples from globally distributed sites at the poles and mid-latitudes, to determine the evolutionary relationship between cosmopolitan and endemic phylotypes of snow algae. We further applied a coalescent theory–based demographic model to the DNA sequences. We found that the genus Raphidonema (Trebouxiophyceae) was distributed over both poles and mid-latitude regions and was detected in different ice core layers, corresponding to distinct time periods. Our results indicate that the modern cosmopolitan phylotypes belonging to Raphidonema were persistently present long before the last glacial period. Furthermore, endemic phylotypes originated from ancestral cosmopolitan phylotypes, suggesting that modern regional diversity of snow algae in the cryosphere is a product of microevolution. These findings suggest that the cosmopolitans dispersed across the world and then derived new localized endemics, which thus improves our understanding of microbial community formation by microevolution in natural environments.

DOI： 10.1038/s41396-023-01359-3

DOI： 10.1038/s41396-023-01359-3

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PubMed

Other Link： https://www.nature.com/articles/s41396-023-01359-3

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

ABSTRACT

Regional offsets from Northern Hemisphere radiocarbon (¹⁴C) calibration curves are widely recognized for monsoon Asia and often hinder accurate ¹⁴C dating. In this paper, we explore the possible linkage between summer monsoon intensity and ¹⁴C offsets using tree-ring δ¹⁸O and ¹⁴C data from Thailand. We developed a 297-yr floating tree-ring δ¹⁸O chronology comprising seven teak log-coffin samples from the Ban Rai rock shelter site, northwestern Thailand. The outermost ring of our chronology was estimated to date from 358–383 CE, within a 95.4% (2σ) probability range, based on a total of 10 ¹⁴C measurements that were wiggle-matched against a mixed calibration curve evenly weighted from the IntCal20 and SHCal20 curves. Backward trajectory analysis showed that an intensified (weakened) summer monsoon detected in a modern tree-ring δ¹⁸O chronology was most likely to be induced by increased (decreased) air mass transport from the tropical Indian Ocean, which is an area of intense upwelling where the ¹⁴C concentration is lower than the atmospheric ¹⁴C level. However, partly because of the limited sample size and dating uncertainty, the direct linkage between the tree-ring δ¹⁸O series and ¹⁴C records obtained from our teak log-coffin samples could not be statistically verified.

DOI： 10.1017/RDC.2023.14

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Meteorological Society  

Abstract

The mass budget of southern Patagonian glaciers is characterized by an extreme amount of surface ablation. To understand the processes controlling surface mass balance, we analyzed in situ data including meteorological variables and ablation stakes for the 25 years between 1996 and 2020 near the terminus of Glaciar Perito Moreno in southern Patagonia in South America. The mean annual temperature has increased over the study period at a rate of 0.2°C decade⁻¹. An energy-balance model was applied to calculate a point surface mass balance, based on meteorological records. The average point surface mass balance is estimated to be −16.3 m water equivalent (w.e.) yr⁻¹ between 1996 and 2020, decreasing at a rate in the range from −0.4 to −0.9 m w.e. yr⁻¹ decade⁻¹. The greatest contribution to the surface energy balance was due to the sensible heat flux, and its variation drove the surface mass balance variation. The meteorological and surface mass balance records were compared with the Southern Annular Mode and El Niño–Southern Oscillation, which change the atmospheric circulation over southern Patagonia and influence surface mass balance near the terminus of the glacier. Our long-term dataset investigates the detailed meteorological conditions and surface mass balance and their connection with the large-scale climate variability over the last 25 years, reported for the first time in Patagonia.

DOI： 10.1175/JCLI-D-22-0294.1

DOI： 10.1175/jcli-d-22-0294.1

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Other Link： https://journals.ametsoc.org/downloadpdf/journals/clim/36/2/JCLI-D-22-0294.1.xml

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Ocean phytoplankton are an important source of dimethyl sulfide, which influences marine cloud formation. Model studies suggest that declines in Arctic sea ice may lead to increased dimethyl sulfide emissions, however observational support is lacking. Here, we present a 55-year high-resolution ice core record of methane sulfonic acid flux, an oxidation product of dimethyl sulfide, from the southeast Greenland Ice Sheet. We infer temporal variations in ocean dimethyl sulfide emissions and find that springtime (April–June) fluxes of methane sulfonic acid correlate well with satellite-derived chlorophyll-a concentration in the Irminger Sea. Summertime (July–September) methane sulfonic acid fluxes were 3 to 6 times higher between 2002–2014 than 1972–2001. We attribute this to sea ice retreat day becoming earlier and a coincident increase in chlorophyll-a concentration in the adjacent open coastal waters.

DOI： 10.1038/s43247-022-00661-w

DOI： 10.1038/s43247-022-00661-w

Web of Science

Other Link： https://www.nature.com/articles/s43247-022-00661-w

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

Glacier health across High Mountain Asia (HMA) is highly heterogeneous and strongly governed by regional climate, which is variably influenced by monsoon dynamics and the westerlies. We explore four decades of glacier energy and mass balance at three climatically distinct sites across HMA by utilising a detailed land surface model driven by bias-corrected Weather Research and Forecasting meteorological forcing. All three glaciers have experienced long-term mass losses (ranging from −0.04 ± 0.09 to −0.59 ± 0.20 m w.e. a⁻¹) consistent with widespread warming across the region. However, complex and contrasting responses of glacier energy and mass balance to the patterns of the Indian Summer Monsoon were evident, largely driven by the role snowfall timing, amount and phase. A later monsoon onset generates less total snowfall to the glacier in the southeastern Tibetan Plateau during May–June, augmenting net shortwave radiation and affecting annual mass balance (−0.5 m w.e. on average compared to early onset years). Conversely, timing of the monsoon’s arrival has limited impact for the Nepalese Himalaya which is more strongly governed by the temperature and snowfall amount during the core monsoon season. In the arid central Tibetan Plateau, a later monsoon arrival results in a 40 mm (58%) increase of May–June snowfall on average compared to early onset years, likely driven by the greater interaction of westerly storm events. Meanwhile, a late monsoon cessation at this site sees an average 200 mm (192%) increase in late summer precipitation due to monsoonal storms. A trend towards weaker intensity monsoon conditions in recent decades, combined with long-term warming patterns, has produced predominantly negative glacier mass balances for all sites (up to 1 m w.e. more mass loss in the Nepalese Himalaya compared to strong monsoon intensity years) but sub-regional variability in monsoon timing can additionally complicate this response.

DOI： 10.1088/1748-9326/ac9008

DOI： 10.1088/1748-9326/ac9008

Web of Science

Other Link： https://iopscience.iop.org/article/10.1088/1748-9326/ac9008/pdf

Language：English  

DOI： 10.3389/feart.2022.1021292

DOI： 10.3389/feart.2022.1021292

Web of Science

Other Link： https://www.frontiersin.org/articles/10.3389/feart.2022.1021292/full

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. There have been rapid increases in both the number andexpansion of the proglacial lakes across High Mountain Asia. However, therelationship between proglacial lakes and glacier dynamics remains unclearin the Himalayan region. Here we present the surface elevation, flow-velocity changes, and proglacial lake expansion of Thorthormi and Luggeglaciers in the Lunana region, Bhutanese Himalaya, during the 2000–2018period using photogrammetry and GPS survey data. The lake expansion andsurface lowering rates and flow-velocity field of Lugge Glacier, alake-terminating glacier, have remained approximately constant since 2000.Conversely, there have been accelerated proglacial lake expansion and a2-fold increase in the thinning rate of Thorthormi Glacier since 2011, aswell as a considerable speed-up in the flow-velocity field(>150 m a−1). We reveal that the lake formation and transition of ThorthormiGlacier from a land- to lake-terminating glacier have triggered glacierspeed-up and rapid thinning via a positive (compressive) to negative(extensional) change in the emergence velocities. This study provides thefirst evidence of dynamic glacier changes that are associated withproglacial lake formation across the Himalayan region.

DOI： 10.5194/tc-16-2643-2022

DOI： 10.5194/tc-16-2643-2022

Web of Science

Other Link： https://tc.copernicus.org/articles/16/2643/2022/tc-16-2643-2022.pdf

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

This study describes the <italic>in situ</italic> observed and modeled mass balances of four representative glaciers in the Mongolian Altai Mountains. Mass-balance stakes and automatic weather stations (AWS) were installed along each glacier to obtain the <italic>in situ</italic> mass balances and meteorological variables. We calibrate the ERA5 meteorological variables using the observed values, then estimate the precipitation parameters to obtain the observed point mass balances using an energy- and mass-balance model. We evaluate the mass-balance profile and glacier-wide mass balance via a mass-balance model using the calibrated ERA5 data and estimated precipitation parameters to fill in the spatial and temporal gaps in the stake networks and AWS measurements. We demonstrate that almost all of the observed mass balances have been in a negative state since 2003. We also reconstruct the long-term mass balances for the 1980–2018 period, which range from −760 to −160 mm water equivalent under the different climatic conditions (annual precipitation varies from 190 to 860 mm). We further evaluate the mass-balance sensitivities to temperature and precipitation changes. We confirm that both sensitivities correlate significantly with the annual precipitation; increased precipitation yields more negative sensitivity to temperature changes and less positive sensitivity to precipitation changes.

DOI： 10.3389/feart.2021.785306

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.epsl.2021.117299

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

<title>Abstract</title>We drilled an 81.2-m-long ice core in the accumulation area (5860 m a.s.l.) of Trambau Glacier in the Rolwaling region during October–November 2019. The drilling operation was conducted with a lightweight electro-mechanical drill system after two reconnaissance fieldworks in 2017 and 2018, during which two shallow firn cores were drilled with a hand auger. The drill system and ice core samples were transported by helicopters at a high elevation of 6000 m a.s.l. A further challenging issue was the ice core transportation between Nepal and Japan, as no regular commercial flight was available for the frozen samples. The addition of dry ice imported from India immediately prior to leaving Nepal allowed the ice core samples to be successfully transported to a cold room in Japan, and remain in a frozen state. Stratigraphic observations during the drilling operation suggest the drill site has been affected by melting and refreezing.

DOI： 10.1017/aog.2021.15

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2021GL093808

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021GL093808

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2020JD034255

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020JD034255

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Previous reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA-Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time-invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.

DOI： 10.1029/2020EA001590

Web of Science

Scopus

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020EA001590

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Our study is the first to demonstrate a
high-temporal-resolution record of mineral composition in a Greenland ice
core over the past 100 years. To reconstruct past variations in the sources
and transportation processes of mineral dust in northwestern Greenland, we
analysed the morphology and mineralogical composition of dust in the SIGMA-D
ice core from 1915 to 2013 using scanning electron microscopy (SEM) and
energy-dispersive X-ray spectroscopy (EDS). The results revealed that the
ice core dust consisted mainly of silicate minerals and that the composition
varied substantially on multi-decadal and inter-decadal scales, suggesting
that the ice core minerals originated from different geological sources in
different periods during the past 100 years. The multi-decadal variation
trend differed among mineral types. Kaolinite, which generally formed in
warm and humid climatic zones, was abundant in colder periods (1950–2004),
whereas mica, chlorite, feldspars, mafic minerals, and quartz, which
formed in arid, high-latitude, and local areas, were abundant in warmer
periods (1915–1949 and 2005–2013). Comparison to Greenland surface
temperature records indicates that multi-decadal variation in the relative
abundance of these minerals was likely affected by local temperature changes
in Greenland. Trajectory analysis shows that the minerals were transported
mainly from the western coast of Greenland in the two warming periods, which
was likely due to an increase in dust sourced from local ice-free areas as a
result of shorter snow/ice cover duration in the Greenland coastal region
during the melt season caused by recent warming. Meanwhile, ancient deposits
in northern Canada, which were formed in past warmer climates, seem to be the
best candidate during the colder period (1950–2004). Our results suggest
that SEM–EDS analysis can detect variations in ice core dust sources during
recent periods of low dust concentration.

DOI： 10.5194/cp-17-1341-2021

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Ice cliffs can act as “hot spots” for melt on debris-covered glaciers and promote local glacier mass loss. Repeat high-resolution remote-sensing data are therefore required to monitor the role of ice cliff dynamics in glacier mass loss. Here we analyze high-resolution aerial photogrammetry data acquired during the 2007, 2018, and 2019 post-monsoon seasons to delineate and monitor the morphology, distribution, and temporal changes of the ice cliffs across the debris-covered Trakarding Glacier in the eastern Nepal Himalaya. We generate an ice cliff inventory from the 2018 and 2019 precise terrain data, with ice cliffs accounting for 4.7 and 6.1% of the debris-covered area, respectively. We observe large surface lowering (&amp;gt;2.0 m a⁻¹) where there is a denser distribution of ice cliffs. We also track the survival, formation, and disappearance of ice cliffs from 2018 to 2019, and find that ∼15% of the total ice cliff area is replaced by new ice cliffs. Furthermore, we observe the overall predominance of northwest-facing ice cliffs, although we do observe spatial heterogeneities in the aspect variance of the ice cliffs (ice cliffs face in similar/various directions). Many new ice cliffs formed across the stagnant middle sections of the glacier, coincident with surface water drainage and englacial conduit intake observations. This spatial relationship between ice cliffs and the glacier hydrological system suggests that these englacial and supraglacial hydrological systems play a significant role in ice cliff formation.

DOI： 10.3389/feart.2021.623623

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Efficient statistical emulation of melting land ice under various climate scenarios to 2100 indicates a contribution from melting land ice to sea level increase of at least 13 centimetres sea level equivalent.The land ice contribution to global mean sea level rise has not yet been predicted(1) using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models(2-8), but primarily used previous-generation scenarios(9) and climate models(10), and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios(11,12) using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.

DOI： 10.1038/s41586-021-03302-y

Web of Science

PubMed

Other Link： http://www.nature.com/articles/s41586-021-03302-y

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

After the 1980s, atmospheric sulfate reduction is slower than the dramatic reductions in sulfur dioxide (SO₂) emissions. However, a lack of observational evidence has hindered the identification of causal feedback mechanisms. Here, we report an increase in the oxygen isotopic composition of sulfate (<inline-formula><m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:semantics definitionURL="" encoding=""><m:mrow><m:msup><m:mi mathvariant="normal">Δ</m:mi><m:mn>17</m:mn></m:msup><m:msub><m:mi mathvariant="normal">O</m:mi><m:mrow><m:msubsup><m:mi mathvariant="normal">SO</m:mi><m:mn>4</m:mn><m:mrow><m:mn>2</m:mn><m:mo>−</m:mo></m:mrow></m:msubsup></m:mrow></m:msub></m:mrow><m:annotation encoding="" /></m:semantics></m:math></inline-formula>) in a Greenland ice core, implying an enhanced role of acidity-dependent in-cloud oxidation by ozone (up to 17 to 27%) in sulfate production since the 1960s. A global chemical transport model reproduces the magnitude of the increase in observed <inline-formula><m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:semantics definitionURL="" encoding=""><m:mrow><m:msup><m:mi mathvariant="normal">Δ</m:mi><m:mn>17</m:mn></m:msup><m:msub><m:mi mathvariant="normal">O</m:mi><m:mrow><m:msubsup><m:mi mathvariant="normal">SO</m:mi><m:mn>4</m:mn><m:mrow><m:mn>2</m:mn><m:mo>−</m:mo></m:mrow></m:msubsup></m:mrow></m:msub></m:mrow><m:annotation encoding="" /></m:semantics></m:math></inline-formula> with a 10 to 15% enhancement in the conversion efficiency from SO₂ to sulfate in Eastern North America and Western Europe. With an expected continued decrease in atmospheric acidity, this feedback will continue in the future and partially hinder air quality improvements.

DOI： 10.1126/sciadv.abd4610

Web of Science

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.polar.2020.100599

Web of Science

Language：Japanese   Publisher：日本雪氷学会  

CiNii Books

Language：Japanese   Publishing type：Research paper (scientific journal)  

J-GLOBAL

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Snow and Ice  

DOI： 10.5331/bgr.21R01

Web of Science

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.15094/00016228

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Observations and models agree that the Greenland Ice Sheet (GrIS)
surface mass balance (SMB) has decreased since the end of the 1990s due to
an increase in meltwater runoff and that this trend will accelerate in the
future. However, large uncertainties remain, partly due to different
approaches for modelling the GrIS SMB, which have to weigh physical
complexity or low computing time, different spatial and temporal
resolutions, different forcing fields, and different ice sheet
topographies and extents, which collectively make an inter-comparison
difficult. Our GrIS SMB model intercomparison project (GrSMBMIP) aims to
refine these uncertainties by intercomparing 13 models of four types which
were forced with the same ERA-Interim reanalysis forcing fields, except for
two global models. We interpolate all modelled SMB fields onto a common ice
sheet mask at 1 km horizontal resolution for the period 1980–2012 and score
the outputs against (1) SMB estimates from a combination of gravimetric
remote sensing data from GRACE and measured ice discharge; (2) ice cores,
snow pits and in situ SMB observations; and (3) remotely sensed bare ice extent
from MODerate-resolution Imaging Spectroradiometer (MODIS). Spatially, the
largest spread among models can be found around the margins of the ice
sheet, highlighting model deficiencies in an accurate representation of the
GrIS ablation zone extent and processes related to surface melt and runoff.
Overall, polar regional climate models (RCMs) perform the best compared to
observations, in particular for simulating precipitation patterns. However,
other simpler and faster models have biases of the same order as RCMs
compared with observations and therefore remain useful tools for long-term
simulations or coupling with ice sheet models. Finally, it is interesting to
note that the ensemble mean of the 13 models produces the best estimate of
the present-day SMB relative to observations, suggesting that biases are not
systematic among models and that this ensemble estimate can be used as a
reference for current climate when carrying out future model developments.
However, a higher density of in situ SMB observations is required,
especially in the south-east accumulation zone, where the model spread can
reach 2 m w.e. yr−1 due to large discrepancies in modelled snowfall accumulation.

DOI： 10.5194/tc-14-3935-2020

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2019EF001470

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2019EF001470

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. In cold and arid climates, small glaciers with cold accumulation
zones are often thought to be entirely cold based. However, scattering in
ground-penetrating radar (GPR) measurements on the Rikha Samba Glacier in
the Nepal Himalayas suggests a large amount of temperate ice that seems to
be influenced by the presence of crevassed areas. We used a coupled
thermo-mechanical model forced by a firn model accounting for firn heating
to interpret the observed thermal regime. Using a simple energy conservation
approach, we show that the addition of water percolation and refreezing in
crevassed areas explains these observations. Model experiments show that
both steady and transient thermal regimes are significantly affected by
latent heat release in crevassed areas. This makes half of the glacier base
temperate, resulting in an ice dynamic mainly controlled by basal friction
instead of ice deformation. The timescale of thermal regime change, in
response to atmospheric warming, is also greatly diminished, with a
potential switch from cold to temperate basal ice in 50–60 years in the
upper part of the glacier instead of the 100–150 years that it would take
without the effect of the crevasses. This study highlights the crucial role
of water percolation through the crevasses on the thermal regime of glaciers
and validates a simple method to account for it in glacier thermo-mechanical
models.

DOI： 10.5194/tc-14-1273-2020

Web of Science

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

Despite the importance of glacial lake development in ice dynamics and glacier thinning, in situ and satellite-based measurements from lake-terminating glaciers are sparse in the Bhutanese Himalaya, where a number of proglacial lakes exist. We acquired in situ and satellite-based observations across lake- and land-terminating debris-covered glaciers in the Lunana region, Bhutanese Himalaya. A repeated differential global positioning system survey reveals that thickness change of the debris-covered ablation area of the lake-terminating Lugge Glacier (-4.67 +/- 0.07 m a(-1)) is more than 3 times more negative than that of the land-terminating Thorthormi Glacier (-1 40 +/- 0.07 m a(-1)) for the 2004-2011 period. The surface flow velocities decrease down-glacier along Thorthormi Glacier, whereas they increase from the upper part of the ablation area to the terminus of Lugge Glacier. Numerical experiments using a two-dimensional ice flow model demonstrate that the rapid thinning of Lugge Glacier is driven by both a negative surface mass balance and dynamically induced ice thinning. However, the thinning of Thorthormi Glacier is minimised by a longitudinally compressive flow regime. Multiple supraglacial ponds on Thorthormi Glacier have been expanding since 2000 and have merged into a single proglacial lake, with the glacier terminus detaching from its terminal moraine in 2011. Numerical experiments suggest that the thinning of Thorthormi Glacier will accelerate with continued proglacial lake development.

DOI： 10.5194/tc-13-2733-2019

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

We conducted a mass-balance study of debris-free Trambau Glacier in the Rolwaling region, Nepal Himalaya, which is accessible to 6000 m a.s.l., to better understand mass-balance processes and the effect of precipitation on these processes on high-elevation Himalayan glaciers. Continuous in situ meteorological and mass-balance observations that spanned the three melt seasons from May 2016 are reported. An energy- and mass-balance model is also applied to evaluate its performance and sensitivity to various climatic conditions. Glacier-wide mass balances ranging from -0.34 +/- 0.38 m w.e. in 2016 to -0.82 +/- 0.53 m w.e. in 2017/18 are obtained by combining the observations with model results for the areas above the highest stake. The estimated long-term glacier mass balance, which is reconstructed using the ERA-Interim data calibrated with in situ data, is -0.65 +/- 0.39 m w.e. a(-1) for the 1980-2018 period. A significant correlation with annual precipitation (r = 0.77, p < 0.001) is observed, whereas there is no discernible correlation with summer mean air temperature. The results indicate the continuous mass loss of Trambau Glacier over the last four decades, which contrasts with the neighbouring Mera Glacier in balance.

DOI： 10.1017/jog.2019.37

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

© 2019, The Author(s). Marine biogenic sulphur affects Earth’s radiation budget and may be an indicator of primary productivity in the Southern Ocean, which is closely related to atmospheric CO2 variability through the biological pump. Previous ice-core studies in Antarctica show little climate dependence of marine biogenic sulphur emissions and hence primary productivity, contradictory to marine sediment records. Here we present new 720,000-year ice core records from Dome Fuji in East Antarctica and show that a large portion of non-sea-salt sulphate, which was traditionally used as a proxy for marine biogenic sulphate, likely originates from terrestrial dust during glacials. By correcting for this, we make a revised calculation of biogenic sulphate and find that its flux is reduced in glacial periods. Our results suggest reduced dimethylsulphide emissions in the Antarctic Zone of the Southern Ocean during glacials and provide new evidence for the coupling between climate and the Southern Ocean sulphur cycle.

DOI： 10.1038/s41467-019-11128-6

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2018JD030218

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2018JF004848

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2018JF004848

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5194/acp-19-2441-2019

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

© 2018 The Authors We provide continuous records of biomass burning molecular tracers (levoglucosan and dehydroabietic acid) in a Greenland ice core collected from the Southeastern Dome (the SE-Dome ice core) over the past several decades to assess the paleoclimatic utility of these tracers in Greenland ice cores. An air mass backward-trajectory analysis indicates that eastern Canada is likely the primary source region of the biomass burning tracers. Comparisons of levoglucosan and dehydroabietic acid data in the SE-Dome ice core and area burned (vegetation fire) events in Canada suggests that the biomass burning tracers in the ice core document most of the pronounced biomass burning events in eastern Canada over the past several decades, confirming that analyses of biomass burning molecular tracers in Greenland ice cores are useful to reconstruct the frequency of significant biomass burning events in a local region. However, our study also highlights that the wind pattern when the biomass burning occurs is decisive for the registration of a biomass burning event in an ice core even though long-term changes in the wind regime associated with decadal-scale climate oscillations do not significantly influence the transport and deposition of biomass burning tracers on the Greenland ice sheet.

DOI： 10.1016/j.atmosenv.2018.10.012

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Pollen grains are commonly found in ice cores, particularly those from mountain glaciers at low to middle latitudes. Because the release of pollen from flowers has a seasonality and varies among the plant species, pollen concentrations in ice cores are useful for distinguishing annual or seasonal layers and inferring past vegetation near glaciers. We analyzed major pollen grains in an 87-m-deep ice core drilled at the top of the Grigoriev Ice Cap (4563 m.a.s.l.) in the Tien Shan Mountains, Kyrgyz Republic. Microscopy showed that mainly five pollen taxa were contained in the ice core. Their abundance fluctuated with the depth of the core, indicating their seasonal deposition on the ice cap, while the seasonality of the stable isotopes was not particularly clear because of melting and refreezing signatures. Based on the pollen profiles, annual layers were determined back in time to 1780 AD at a depth of 63.6 m; at greater depth, they could not be distinguished due to ice layer thinning in the glacier. The pollen assemblages have gradually changed during the last 220 years and were particularly distinctive in the deeper part, suggesting the drastic change of vegetation in this region during the Holocene.

DOI： 10.1080/15230430.2019.1638202

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/978-3-319-92288-1_7

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2018GL079653

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

Despite the crucial role of cyanobacteria in various ecosystems, little is known about their evolutionary histories, especially microevolutionary dynamics, because of the lack of knowledge regarding their mutation rates. Here we directly estimated cyanobacterial mutation rates based on ancient DNA analyses of ice core samples collected from Kyrgyz Republic that dates back to ~12,500 cal years before present. We successfully sequenced the 16S rRNA and 16S-23S internal transcribed spacer (ITS) region. Two cyanobacterial operational taxonomic units (OTUs) were detected from the ancient ice core samples, and these OTUs are shared with those from the modern glacier surface. The mutation rate of ITS region was estimated by comparing ancient and modern populations, and were at the magnitude of 10-7substitutions/sites/year. By using a model selection framework, we also demonstrated that the ancient sequences from the ice sample were not contaminated from modern samples. Bayesian demographic analysis based on coalescent theory revealed that cyanobacterial population sizes increased over Asia regions during the Holocene. Thus, our results enhance our understanding of the enigmatic timescale of cyanobacterial microevolution, which has the potential to elucidate the environmental responses of cyanobacteria to the drastic climatic change events of the Quaternary.

DOI： 10.1038/s41437-017-0040-3

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

The groundwater recharge mechanism in the hyper-arid Gobi Desert of Northwestern China was analyzed using water balance and tracer-based approaches. Investigations of evaporation, soil water content, and their relationships with individual rainfall events were conducted from April to August of 2004. Water sampling of rainwater, groundwater, and surface water was also conducted. During this period, 10 precipitation events with a total amount of 41.5 mm, including a maximum of 28.9 mm, were observed. Evaporation during the period was estimated to be 33.1 mm. Only the soil water, which was derived from the heaviest precipitation, remained in the vadose zone. This is because a dry surface layer, which was formed several days after the heaviest precipitation event, prevented evaporation. Prior to that, the heaviest precipitation rapidly infiltrated without being affected by evaporation. This is corroborated by the isotopic evidence that both the heaviest precipitation and the groundwater retained no trace of significant kinetic evaporation. Estimated δ-values of the remaining soil water based on isotopic fractionation and its mass balance theories also demonstrated no trace of kinetic fractionation in the infiltration process. Moreover, stable isotopic compositions of the heaviest precipitation and the groundwater were very similar. Therefore, we concluded that the high-intensity precipitation, which rapidly infiltrated without any trace of evaporation, was the main source of the groundwater.

DOI： 10.3390/environments5050055

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 through glacial cycles. However, these variables display a puzzling asynchrony. Well-dated records of Southern Ocean temperature will provide crucial information because the Southern Ocean is likely key in regulating CO2 variations. Here, we perform multiple isotopic analyses on an Antarctic ice core and estimate temperature variations at this site and in the oceanic moisture source over the past 720,000 years, which extend the longest records by 300,000 years. Antarctic temperature is affected by large variations in local insolation that are induced by obliquity. At the obliquity periodicity, the Antarctic and ocean temperatures lag annual mean insolation. Further, the magnitude of the phase lag is minimal during low eccentricity periods, suggesting that secular changes in the global carbon cycle and the ocean circulation modulate the phase relationship among temperatures, CO2 and insolation in the obliquity frequency band.

DOI： 10.1038/s41467-018-03328-3

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

To improve surface mass balance (SMB) estimates for the Greenland Ice Sheet (GrIS), we developed a 5ĝ€̄km resolution regional climate model combining the Japan Meteorological Agency Non-Hydrostatic atmospheric Model and the Snow Metamorphism and Albedo Process model (NHM-SMAP) with an output interval of 1ĝ€̄h, forced by the Japanese 55-year reanalysis (JRA-55). We used in situ data to evaluate NHM-SMAP in the GrIS during the 2011-2014 mass balance years. We investigated two options for the lower boundary conditions of the atmosphere: an offline configuration using snow, firn, and ice albedo, surface temperature data from JRA-55, and an online configuration using values from SMAP. The online configuration improved model performance in simulating 2ĝ€̄m air temperature, suggesting that the surface analysis provided by JRA-55 is inadequate for the GrIS and that SMAP results can better simulate physical conditions of snow/firn/ice. It also reproduced the measured features of the GrIS climate, diurnal variations, and even a strong mesoscale wind event. In particular, it successfully reproduced the temporal evolution of the GrIS surface melt area extent as well as the record melt event around 12 July 2012, at which time the simulated melt area extent reached 92.4ĝ€̄%. Sensitivity tests showed that the choice of calculation schemes for vertical water movement in snow and firn has an effect as great as 200ĝ€̄Gtĝ€̄year-1 in the GrIS-wide accumulated SMB estimates
a scheme based on the Richards equation provided the best performance.

DOI： 10.5194/tc-12-635-2018

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press  

We present a comprehensive review of the status and changes in glacier length (since the 1850s), area and mass (since the 1960s) along the Himalayan-Karakoram (HK) region and their climate-change context. A quantitative reliability classification of the field-based mass-balance series is developed. Glaciological mass balances agree better with remotely sensed balances when we make an objective, systematic exclusion of likely flawed mass-balance series. The Himalayan mean glaciological mass budget was similar to the global average until 2000, and likely less negative after 2000. Mass wastage in the Himalaya resulted in increasing debris cover, the growth of glacial lakes and possibly decreasing ice velocities. Geodetic measurements indicate nearly balanced mass budgets for Karakoram glaciers since the 1970s, consistent with the unchanged extent of supraglacial debris-cover. Himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short-wave radiation balance. Melt contributions from HK glaciers should increase until 2050 and then decrease, though a wide range of present-day area and volume estimates propagates large uncertainties in the future runoff. This review reflects an increasing understanding of HK glaciers and highlights the remaining challenges.

DOI： 10.1017/jog.2017.86

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

©2017. American Geophysical Union. All Rights Reserved. The Southeastern Greenland Dome (SE-Dome) has both a high elevation and a high accumulation rate (1.01 m we yr−1), which are suitable properties for reconstructing past environmental changes with a high time resolution. For this study, we measured the major ion fluxes in a 90 m ice core drilled from the SE-Dome region in 2015 and present the records of annual ion fluxes from 1957 to 2014. From 1970 to 2010, the trend of nonsea-salt (nss) SO42− flux decreases, whereas that for NH4+ increases, tracking well with the anthropogenic SOx and NH3 emissions mainly from North America. The result suggests that these fluxes reflect histories of the anthropogenic SOx and NH3 emissions. In contrast, the decadal trend of NO3− flux differs from the decreasing trend of anthropogenic NOx emissions. Although the cause of this discrepancy remains unclear, it may be related to changes in particle formation processes and chemical scavenging rates caused by an increase in sea salt and dust and/or a decrease in nssSO42−. We also find a high average NO3− flux (1.13 mmol m−2 yr−1) in the ice core, which suggests a negligible effect from postdepositional NO3− loss. Thus, the SE-Dome region is an excellent location for reconstructing nitrate fluxes. Over a decadal time scale, our NO3− flux record is similar to those from other ice cores in Greenland high-elevation sites, suggesting that NO3− concentration records from these ice cores are reliable.

DOI： 10.1002/2017JD026733

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Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

This study presents the geodetic mass balance of Kanchenjunga Glacier, one of the largest debris-covered glaciers in the easternmost Nepal Himalaya, which possesses a negative mass balance of -0.18 +/- 0.17mw.e.a(-1) for the 1975-2010 study period, estimated using digital elevation models (DEMs) generated from Hexagon KH-9 and ALOS PRISM stereo images. Accurate DEMs, with a relative uncertainty of +/- 5.5 m, were generated from the intensive and manual editing of triangulated irregular network (TIN) models on a stereo MirrorTM/3D Monitor. The glacier ice-flow velocity field was also calculated using a feature-tracking method that was applied to two ALOS orthoimages taken in 2010. The elevation differences between the two DEMs highlight considerable surface lowering across the debriscovered area, and a slight thickening in the accumulation area of Kanchenjunga Glacier between 1975 and 2010. The magnitude and gradient of surface lowering are similar among the six glacier tributaries, even though they are situated at different elevations, which may reflect variations in the iceflow velocity field. The pattern of surface lowering correlates well with the ice-flow velocity field over the debriscovered portion of the main tributary, suggesting that the glacier dynamics significantly affect surface lowering by altering the emergence velocity along the glacier, particularly in the compressive ablation area. Surface-lowering patterns partially correspond to the supraglacial pond area fraction of the glacier, with enhanced surface lowering observed in areas that possess a larger pond area fraction. These findings support the hypothesis that supraglacial ponds may intensify ice wastage and play a key role in the heterogeneous surface lowering of debris-covered glaciers. The estimated mass loss of Kanchenjunga Glacier is moderate compared with other debris-covered glaciers in neighboring Himalayan regions, which may be due to the lower pond area fraction of Kanchenjunga Glacier relative to other glaciers.

DOI： 10.5194/tc-11-2815-2017

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

A precise age scale based on annual layer counting is essential for investigating past environmental changes from ice core records. However, subannual scale dating is hampered by the irregular intraannual variabilities of oxygen isotope (delta O-18) records. Here we propose a dating method based on matching the delta O-18 variations between ice core records and records simulated by isotope-enabled climate models. We applied this method to a new delta O-18 record from an ice core obtained from a dome site in southeast Greenland. The close similarity between the delta O-18 records from the ice core and models enables correlation and the production of a precise age scale, with an accuracy of a few months. A missing delta O-18 minimum in the 1995/1996 winter is an example of an indistinct delta O-18 seasonal cycle. Our analysis suggests that the missing delta O-18 minimum is likely caused by a combination of warm air temperature, weak moisture transport, and cool ocean temperature. Based on the age scale, the average accumulation rate from 1960 to 2014 is reconstructed as 1.02 m yr(-1) in water equivalent. The annual accumulation rate shows an increasing trend with a slope of 3.6 mm yr(-1), which is mainly caused by the increase in the autumn accumulation rate of 2.6 mm yr(-1). This increase is likely linked to the enhanced hydrological cycle caused by the decrease in Arctic sea ice area. Unlike the strong seasonality of precipitation amount in the ERA reanalysis data in the southeast dome region, our reconstructed accumulation rate suggests a weak seasonality.

DOI： 10.1002/2017JD026716

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Recent studies of Asian glaciers have shown that glaciers in eastern Karakoram and West Kunlun have been slightly gaining mass while those in nearby Jammu Kashmir and Himalayas are losing mass, at rates of more than 0.5 m w.e.yr(-1) and about 0.3 m w.e.yr-1, respectively. Two possible explanations have been proposed for this difference in glacier behaviour: spatial heterogeneity in climate change (climatic forcing) or differing glacier responses to climate change (glacier response). However, neither explanation has strong supporting evidence. Here, we examine the glacial response by calculating the mass-balance sensitivity to temperature change in high-mountain Asia. In support of the glacier-response explanation, we find a strong correlation between observed glacier surface-elevation changes and mass-balance sensitivity of glaciers. The high coefficient of determination (R-2 = 0.61) suggests that spatially heterogeneous mass-balance sensitivity has more explanatory power than regionally different climate change for the recent contrasting glacier fluctuations in the high mountain Asia.

DOI： 10.1038/s41598-017-14256-5

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Despite the widespread shrinkage of debris-covered Himalayan glaciers in recent decades, the underlying processes driving these changes are poorly understood. This study presents recent mass-balance data for the debris-covered area of Lirung Glacier in Langtang Valley, Nepal Himalaya, constrained using multi-temporal, remotely sensed digital elevation models calibrated to in situ GPS survey data, and surface-flow velocity data from phase-only correlation. The results indicate surface lowering of between -1.3 and -1.8 m a(-1) during the study period ( 1974-2010), with accelerated glacier thinning after 2000. Similarly, we observed a decline in emergence velocity in the upper debris-covered area since 2000. We argue that this deceleration plays a key role in surface lowering, in contrast to declining surface mass balance, which we suggest is a residual effect of emergence velocity and surface lowering. Taken together, our findings indicate that the recent increase in surface lowering is attributable to the declining flux of ice from the upper to lower debris-covered areas of Lirung Glacier. Furthermore, this pattern suggests that downwasting of the upper debris-covered area will be augmented by a positive feedback between surface lowering and decelerated flow velocity. (C) 2017 Elsevier Ltd and INQUA. All rights reserved.

DOI： 10.1016/j.quaint.2017.06.066

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

To better understand the influence of topography on the formation of Himalayan debris-covered glaciers, we manually digitized 5301 glaciers, covering an area of 5691 +/- 893 km(2), from high-resolution Advanced Land Observing Satellite imagery, and identified 842 debris-covered glaciers with a debris-covered area of 3839 +/- 753 km(2). This estimation of the debris-covered area of these glaciers is a novel approach in the Eastern Himalayas. We investigated the relationship between the debris-covered area and the corresponding potential debris supply (PDS) slopes for the debris-covered glaciers across the region. The PDS slopes on the southern side show better correlation with their debris-covered area formation than those situated on the northern side of the Himalayan barrier, with this correlation weakening toward the western massifs. Further investigation showed that PDS slopes oriented SE to Wexert a stronger control on the formation of debris-covered areas, which is related to the diurnal freezeethaw cycle on the southern slope of the mountain barrier. (C) 2017 Elsevier Ltd and INQUA. All rights reserved.

DOI： 10.1016/j.quaint.2017.08.007

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

A comprehensive glacier-glacial lake inventory was developed for the Bhutan Himalayas based on satellite observations between 1987-1990 and 2006-2011. In total, 733 lakes (covering 82.6 km(2)) were delineated between 4000 and 6000 m a.s.l. and their relationships to associated glaciers were documented. Using this new inventory, the scale and potential for glacial lake outburst flooding (GLOF) based on multiple criteria was examined. This included a history of connectivity characteristics of glacial lakes to mother glaciers, potential flood volumes, and debris-cover of mother glaciers in addition to the conventional criteria of expansion rate and lake size. The majority of the lakes with high expansion rates (more than double in size) and large areas (> 0.1 km(2)) met the conditions of being continuously in contact with a mother debris-covered glacier for nearly 20 years. Based on these multiple criteria, two lakes were identified as having potential for large-scale GLOF. Potentially dangerous glacial lakes listed in the International Centre for Integrated Mountain Development (ICIMOD) study were re-visited, and some overlaps with the glacier-glacial lake inventory were found.

DOI： 10.3390/geosciences7030077

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

What are the main morphological factors that control the heterogeneous responses of debris covered glaciers to climate change in the southern central Himalaya? A debate is open whether thinning rates on debris covered glaciers are comparable to those of debris free ones. Previous studies have adopted a deterministic approach, which is indispensable, but is also limiting in that only a few glaciers can be monitored. In this context, we propose a statistical analysis based on a wider glacier population as a complement to these deterministic studies. We analysed 28 glaciers situated on the southern slopes of Mt. Everest in the central southern Himalaya during the period 1992-2008. This study combined data compiled by three distinct studies for a common period and population of glaciers for use in a robust statistical analysis. Generally, surface gradient was the main morphological factor controlling the features and responses of the glaciers to climate change. In particular, the key points that emerged are as follows. 1) Reduced downstream surface gradient is responsible for increased glacier thinning. 2) The development of supraglacial ponds is a further controlling factor of glacier thinning: where supraglacial ponds develop, the glaciers register further surface lowering. 3) Debris coverage and thickness index were not found to be significantly responsible for the development of supraglacial ponds, changes in elevation, or shifts in snow line altitude. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2017.04.039

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

Coseismic avalanches and rockfalls, as well as their simultaneous air blast and muddy flow, which were induced by the 2015 Gorkha earthquake in Nepal, destroyed the village of Langtang. In order to reveal volume and structure of the deposit covering the village, as well as sequence of the multiple events, we conducted an intensive in situ observation in October 2015. Multitemporal digital elevation models created from photographs taken by helicopter and unmanned aerial vehicles reveal that the deposit volumes of the primary and succeeding events were 6.81 +/- 1.54 x 10(6) and 0.84 +/- 0.92 x 10(6) m(3), respectively. Visual investigations of the deposit and witness statements of villagers suggest that the primary event was an avalanche composed mostly of snow, while the collapsed glacier ice could not be dominant source for the total mass. Succeeding events were multiple rockfalls which may have been triggered by aftershocks. From the initial deposit volume and the area of the upper catchment, we estimate an average snow depth of 1.82 +/- 0.46m in the source area. This is consistent with anomalously large snow depths (1.28-1.52 m) observed at a neighboring glacier (4800-5100ma.s.l.), which accumulated over the course of four major snowfall events between October 2014 and the earthquake on 25 April 2015. Considering long-term observational data, probability density functions, and elevation gradients of precipitation, we conclude that this anomalous winter snow was an extreme event with a return interval of at least 100 years. The anomalous winter snowfall may have amplified the disastrous effects induced by the 2015 Gorkha earthquake in Nepal.

DOI： 10.5194/nhess-17-749-2017

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future change. We investigate the long-term characteristics of climatic variability using a new ice-core record from Dome Fuji, East Antarctica, combined with an existing long record from the Dome C ice core. Antarctic warming events over the past 720,000 years are most frequent when the Antarctic temperature is slightly below average on orbital time scales, equivalent to an intermediate climate during glacial periods, whereas interglacial and fully glaciated climates are unfavourable for a millennial-scale bipolar seesaw. Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instabilitywith bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets.

DOI： 10.1126/sciadv.1600446

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ARCTIC ALPINE RES  

We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was-20.9 degrees C at 20 m depth, and the core gives an average accumulation rate of 1.0 m w.e. yr(-1) in water equivalent. However, the close-off density of 830 kg m(-3) occurs at 83.4-86.8 m depth, which is about 20-m shallower than that obtained from two empirical models. Where the density p &gt; 750 kg m(-3), the densification appears faster than that from the empirical models. As a result, compared to the empirical coefficient, the actual compactive viscosity coefficient is nonlinear and decreases at p &gt; 750 kg m(-3), indicating that the fun with a higher density is softer than that from the empirical result. We argue here that the high accumulation rate creates a high overburden pressure in a short time. Thus, the relative softness of the firn may arise from (1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, (2) the dislocation density in the firn being relatively high.

DOI： 10.1657/AAAR0016-034

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5194/acp-16-6883-2016

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DOI： 10.1017/jog.2016.61

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DOI： 10.1017/jog.2016.34

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DOI： 10.1016/j.polar.2015.12.003

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DOI： 10.1007/s11430-015-5118-2

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DOI： 10.1126/science.aac8353

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DOI： 10.5194/tc-10-65-2016

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DOI： 10.3189/2016AoG71A036

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DOI： 10.3189/2015JoG15J017

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DOI： 10.5194/tc-9-865-2015

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DOI： 10.5194/tc-9-849-2015

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DOI： 10.1016/j.quascirev.2014.09.006

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DOI： 10.1002/2014JD021686.

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DOI： 10.5194/hess-18-2679-2014

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/2013JD020771

Authorship：Lead author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

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DOI： 10.1002/jgrd.50664

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DOI： 10.5194/tc-7-1303-2013

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DOI： 10.5194/nhess-13-1827-2013

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DOI： 10.3189/2013AoG64A111

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DOI： 10.3189/2013JoG12J152

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DOI： 10.1657/1938-4246-45.1.143

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DOI： 10.1088/1748-9326/8/1/014032

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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DOI： 10.3189/2012JoG11J061

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DOI： 0036-8075/1095-9203

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DOI： 10.1007/s12685-012-0057-8

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DOI： 10.1029/2011JD016378

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DOI： 10.3189/002214311798843331

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DOI： 10.5194/tc-5-1057-2011

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DOI： 10.3189/172756411797252293

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DOI： 10.1073/pnas.1106242108

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5194/tc-5-539-2011

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DOI： 10.1657/1938-4246-43.2.246

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DOI： 10.1657/1938-4246-43.1.66

Authorship：Lead author   Language：English  

DOI： 10.1038/471045a

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2010JG001337

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DOI： 10.1029/2010JD013977

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We describe four decades of temporal fluctuations in the ablation of the Hamaguriyuki snow patch in the northern Japan Alps. Annual ablation depth through the melting season shows a significant correlation with the initial depth (at the beginning of the melting season), whereas a less significant correlation is found with a temperature index that is generally believed to correlate well with ablation. The scale effect of the snow patch, which appears to modify the wind speed over the patch, has a more significant effect on snow ablation than does the radiation shadowing effect of surrounding mountains. In the case of a thinner and therefore smaller initial springtime snow patch, the speed of the local wind may be reduced over the snow surface, thereby suppressing ablation, whereas wind speed is not reduced (and ablation is not suppressed) in the case of a thicker snow patch. This self‐regulating feedback means that over the past four decades, the thickness of the snow patch has fluctuated in a manner that is largely independent of summertime temperature. Our findings also suggest that the self‐regulating feedback, which influences ablation, allows some small wind‐drifted glaciers to survive, whereas previous studies reported enhanced accumulation at such glaciers via a similar topographic effect on wind speed and suppressed ablation via the shading effect of surrounding mountains on solar radiation.

Language：English   Publishing type：Research paper (scientific journal)  

Discharge was calculated from a mountainous area, including discharge from glaciers, in the Qilian Shan (Qilian Mountains) of northwest China. The studied Yingluoxia basin is 9983 km2 in area, with glaciers making up 0·3% of the basin. The calculation method was based on the heat balance, requiring only daily temperature and precipitation. Calculated annual discharge from the basin corresponded well with the observed data. Calculated annual discharge from glaciers was 3·6% of the total discharge from the basin.

The temporal trend of the calculated equilibrium line altitude (ELA) at the July 1st Glacier (western side of the Yingluoxia basin) was similar to that of the observed ELA. The calculated annual mass balance of glaciers within the Yingluoxia basin has a larger negative value than the other glaciers in China, as the ratio of accumulation area to the total glacier area in the Yingluoxia basin is much lower than in neighbouring basins to the west.
doi:10.1002/hyp.7700

Authorship：Lead author   Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

High-resolution Antarctic Mesoscale Prediction System archive data were used to investigate high-precipitation events at the deep ice core drilling site Kohnen Station, Dronning Maud Land, Antarctica, during the period 2001–2006. The precipitation is found to be highly episodic, with, on average, approximately eight high-precipitation events per year that can bring more than half of the total annual accumulation. The duration of the events varies between 1 day and about 1 week. On most days in the remaining time of the year, however, daily precipitation sums are about one order of magnitude smaller than that for the high-precipitation events. Synoptic weather patterns causing these events were directly connected to frontal systems of cyclones in only 20% of the 51 investigated cases. The majority of the events occurred in connection with (blocking) anticyclones and correspondingly amplified Rossby waves, which lead to advection of warm, moist air from relatively low latitudes. Possible changes in the seasonality and frequency of these events in a different climate can lead to a bias in ice core properties and might also strongly influence the mass balance of the Antarctic continent and thus global sea level change.
doi:10.1029/2009JD013410

Language：English   Publishing type：Research paper (scientific journal)  

The possible minimal range of reduction in snow surface albedo due to dry deposition of black carbon (BC) in the pre-monsoon period (March–May) was estimated as a lower bound together with the estimation of its accuracy, based on atmospheric observations at the Nepal Climate Observatory – Pyramid (NCO-P) sited at 5079 m a.s.l. in the Himalayan region. A total BC deposition rate was estimated as 2.89 μg m-2 day-1 providing a total deposition of 266 μg m-2 for March–May at the site, based on a calculation with a minimal deposition velocity of 1.0×10-4 m s-1 with atmospheric data of equivalent BC concentration. Main BC size at NCO-P site was determined as 103.1–669.8 nm by correlation analyses between equivalent BC concentration and particulate size distributions in the atmosphere. The BC deposition from the size distribution data was also estimated. It was found that 8.7% of the estimated dry deposition corresponds to the estimated BC deposition from equivalent BC concentration data. If all the BC is deposited uniformly on the top 2-cm pure snow, the corresponding BC concentration is 26.0–68.2 μg kg-1, assuming snow density variations of 195–512 kg m-3 of Yala Glacier close to NCO-P site. Such a concentration of BC in snow could result in 2.0–5.2% albedo reductions. By assuming these albedo reductions continue throughout the year, and then applying simple numerical experiments with a glacier mass balance model, we estimated reductions would lead to runoff increases of 70–204 mm of water. This runoff is the equivalent of 11.6–33.9% of the annual discharge of a typical Tibetan glacier. Our estimates of BC concentration in snow surface for pre-monsoon season is comparable to those at similar altitudes in the Himalayan region, where glaciers and perpetual snow regions begin, in the vicinity of NCO-P. Our estimates from only BC are likely to represent a lower bound for snow albedo reductions, because we used

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Digital elevation models (DEMs) of the ablation area of Hailuogou glacier, China, produced from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data obtained in 2009, differential GPS (DGPS) data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long- and short-term glacier surface elevation change (dh/dt). The mean dh/dt of the ablation area over 43 years (1966-2009) is -1.1 ± 0.4 m a-1. Since 1989 the thinning has accelerated significantly. Ice velocities measured by DGPS at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus, ranging from 41.0 m a-1 approaching the glacier terminus to a maximum of 205.0 m a-1 at the base of an icefall. Our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades. Changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics, which are driven by different factors for different regions and periods.

Language：English   Publishing type：Research paper (scientific journal)  

A 51 m deep ice core was re-drilled on the Dunde Ice Cap of western China in 2002, 15 years after the previous ice core drilling in 1987. Dating by seasonal variations in δ18O and particle concentration showed that this 51 m deep ice core covered approximately the last 150 years. The stratigraphy and density showed that more than 90% of the ice core was refrozen ice layers, which comprised less than 5% of the annual accumulation in the older core. This indicates that the ice cap had experienced a more intense melting since 1987, possibly due to climate warming in this region. Mean net accumulation since the last drilling (2002–1987) was 176 mm a-1, which was considerably smaller than that obtained from the 1987 core (390 mm a-1, 1987–1963), indicating a significant decrease of net accumulation on the ice cap in the more recent period. The δ18O record showed an increasing trend in the late 19th century and the highest in the 1950s, which is consistent with the previous core findings. However, there has been no significant increase in δ18O during the last two decades, in contrast to the warming trends suggested by the melt features and other climate records. This discrepancy may be due to the modification of δ18O records by melt water runoff, percolation, and refreezing on the ice cap. Results strongly suggest recent significant mass loss of glaciers in the Asian high mountains and serious shortage of water supply for local people in this arid region in the near future.

http://www.iop.org/EJ/abstract/1748-9326/4/4/045207

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

The Moon cast a long shadow over Antarctica on 23 November 2003 in a total solar eclipse. The eclipse was observed at Dome Fuji Station, located at the highest point of East Dronning Maud Land, Antarctica, and lasted 1 h 41 min 37 s in a cloudless condition, during which the Sun was completely obscured for 1 min 43 s. This was the first total solar eclipse to be observed in the Antarctic ice sheet. During the eclipse at Dome Fuji, the air temperature at 1.5 m above the snow surface and the subsurface snow temperature decreased by 3.0 K and 1.8 K, respectively. Estimated surface snow temperatures decreased by 4.6 K. Atmospheric pressure and wind direction did not change, but the wind speed possibly decreased by 0.3 m/s with decreasing air temperature; natural variations in wind speed before and after the eclipse made it difficult to identify a true effect of the solar eclipse. Variations of energy components (net shortwave and longwave radiations, sensible and latent heat fluxes, and geothermal heat) during the eclipse were investigated. The total loss of global solar radiation during the eclipse was 0.60 MJ m-2, equaling 1.6% of the total daily global solar radiation. Regional effects of the eclipse due to a reduction of global solar radiation for air temperature and snow temperature ranged from 0.015 to 0.020 K (W m-2)-1. We additionally examined the relation between eclipse obscuration (the fraction of the Sun's surface area occulted by the Moon) and the reduction of global solar radiation from the first to second contacts. The eclipse was also observed from space by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard NASA's Terra and Aqua satellites. The observational results of this study will contribute to detailed model calculations for clarifying the meteorological effects of eclipses.

http://www.agu.org/pubs/crossref/2009/2009JD011886.shtml

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Since ancient times meltwater from glaciers in mountain zones has been an important water resource in the arid region of northwest China. Meteorological elements for heat balance calculations at the glacier surface were simplified with the aim of simulating discharge fluctuations from the July 1st Glacier over a span of decades. By estimating relative humidity and downward solar radiation from precipitation, heat balance calculations at the glacier can be made using only daily temperature and precipitation, which are easily obtainable. Calculations of daily discharge using the above method during the melting season in 2002 produced a better simulation than those using the conventional positive degree-day (PDD) factor method. (The ablation of glacier during any particular period is assumed to be proportional to the sum of daily mean temperatures above the melting point during that period.)
We calculated the glacier runoff and mass balance at the July 1st Glacier since 1935 from monthly meteorological data taken near the glacier using the above method. We used three patterns of daily temperature and precipitation to estimate daily meteorological data from monthly or annual data. Calculated mass balance using the patterns of air temperature and precipitation in years when the pressure distributions were similar to its long-term average corresponded well with observed data. Our simulation of the glacier runoff since 1935 also showed good results.

http://www3.interscience.wiley.com/journal/121574898/abstract

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Numerical calculations are described, aimed at evaluating the influence of precipitation seasonality and seasonality concentration on climatic sensitivity of glacier mass balance. Equilibrium line altitudes (ELAs) are modeled using idealized meteorological variables, and then a warming test (+1 °C) is performed, which revealed that the effects of latitude and the annual precipitation amount are less than those of precipitation seasonality and its concentration. Calculation shows higher sensitivities for the glaciers located in a summer precipitation climate than for those located within a winter-precipitation climate. Difference due to seasonality is enhanced with the seasonality concentration. The present study suggests that the earlier parameterization of glacier mass balance with annual precipitation amount is insufficient to describe the response of glaciers to climate change. Distribution of precipitation seasonality and its concentration suggest that many parts of the world have a summer-precipitation climate but their seasonality concentration is not significant worldwide. On the other hand, an extensive region of Asia and part of the Andes are located in the highly concentrated summer-precipitation climate. This suggests the high sensitivity of glacier mass balance in these regions to climate change.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4TPND5C-1&_user=119029&_coverDate=11/30/2008&_rdoc=3&_fmt=high&_orig=browse&_srch=doc-info(%23toc%235801%232008%23997239998%23701811%23FLA%23display%23Volume)&_cdi=5801&_sort=d&_docanchor=&_ct=25&_acct=C000009318&_version=1&_urlVersion=0&_userid=119029&md5=5e83486055fa5c9d81a457ac60ee1fca

Authorship：Lead author   Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

The mass balance of the Xiao (Lesser) Dongkemadi Glacier located in the Tanggula Mountains, of the central Qinghai-Tibetan Plateau has been monitored since 1989. The results show that the mass balance of the glacier has recently shown a deficit trend, and that the glacial terminus was also retreating. Positive mass balance of the glacier was dominant during the period 1989-1993, and the accumulated mass balance reached 970 mm. However, negative mass balance of the glacier has occurred since 1994, except for the large positive mass balance year 1997. The mass balance was -701 mm in 1998, an extremely negative glacier mass balance year. The equilibrium line altitude showed a significant increasing trend. The mass balance of the glacier has changed from a significantly positive mass balance to a strongly negative mass balance since 1994. Meteorological data suggest that the rapid decrease in the mass balance is related to summer season warming.

http://www3.interscience.wiley.com/journal/116327612/abstract

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Numerical calculations are described, aimed at evaluating the influence of precipitation seasonality (summer and winter) on glacier mass balance. First, equilibrium-line altitudes (ELAs) are modeled using idealized meteorological variables. Modeled climatic conditions (summer mean temperature and annual precipitation) at the ELA of glaciers located within a winter accumulation pattern confirm the observational results of earlier studies. However, the ELA of glaciers located within a summer accumulation climate pattern locates in a colder environment than that of glaciers located within a winter accumulation climate pattern. This difference is mainly due to the annual snow accumulation and the surface albedo. A warming test (+1K) reveals higher sensitivities for the glaciers located within a summer accumulation pattern than for the glaciers located within a winter accumulation pattern. In a humid environment, a significant decrease in snow accumulation on the glaciers located within a summer accumulation pattern directly causes higher sensitivities. In an arid environment, on the other hand, the decreased summer snow induces accelerated melting by lowering the surface albedo and thus increasing absorption of solar radiation on the glaciers located within a summer accumulation pattern. Both influences are due to significant differences in summer precipitation. This study shows the importance of precipitation seasonality on the climatic sensitivity of glacier mass balance, which in previous studies has been linked only with annual precipitation.

http://www.ingentaconnect.com/content/igsoc/agl/2008/00000048/00000001/art00013

Language：Japanese  

第44次南極地域観測隊により,2003年2月1日から2004年1月20日の地上放射観測(短波上向き・下向き,長波上向き・下向き)の結果を報告する.放射計ドームの着霜を回避する目的でファン付き放射計を用いた上向き,下向きの長波放射,及び下向きの短波放射は1997年の観測値と比較的近い値を示し,両年の観測の妥当性を示唆した.しかし,ファンのない放射計を用いた上向き短波放射は,極夜前後の1-2カ月において下向き短波放射を上回るなど,異常値を示している.着霜がこの原因の候補の一つであるが,確かめられない.データの修正については今後の課題とする.また,極夜期の上向き・下向き長波放射について,典型的な地表面放射冷却時期と放射冷却が抑制される時期について,事例を示した.

Language：Japanese  

第44次南極地域観測隊のドームふじ基地におけるシーロメータ観測の結果から,雲及び降雪粒子の鉛直プロファイルの季節変化の概要をまとめ,特徴的な鉛直プロファイルを示した.夏季の2003年2月,12月,及び2004年1月には高度1000m以下に明瞭な雲底が検出される場合が比較的多かった.4月から10月には高度3000mから5000m(標高約7000-9000m)層で夏季より高頻度に雲が観測された.極夜期には高度1500m以下の層でストリーク状の降雪が観測され,これまでの研究と比較し議論した.このストリーク状の降雪は地上に近いほど後方散乱係数が大きくなる特徴を示した.

Language：Japanese  

水の酸素・水素安定同位体（以下，水の安定同位体）を用いた水循環過程に関する重要な研究および最近の研究のレビューを行った．海水の同位体組成（同位体比）に関する知見，同位体大循環モデルを用いた全球スケールの水循環研究，降水形態による同位体比の差異や局域スケールの降水過程に関する研究，流域スケールでの流出過程，植生に関わる蒸発散過程（蒸発と蒸散の分離）の研究をレビューした．加えて，幅広い時間スケールでの気候変動や水循環変動に関する研究として，氷床コアや雪氷コアを利用した古気候・古環境復元とそれらに水の安定同位体を利用した研究についてもレビューした．最後に，水の安定同位体を利用した水循環研究の今後の展望をまとめた．

http://www.jstage.jst.go.jp/article/jjshwr/21/2/21_158/_article/-char/ja/

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

River discharge and groundwater level data were collected in the Heihe River basin, which is the second largest inland river in Northwestern China. The surfacewater-groundwater interaction, particularly in the lower desert reaches, was analyzed with the help of isotope data of water collected from the river. In the non-irrigation period, river water, which originated from the groundwater in the middle oasis reaches, was present throughout the period in the lower desert reaches. During this period, the river water recharged the groundwater not only in the riparian forest region located near the river but also in the desert-riparian fringe region located farther away from the river. In the irrigation period, the river was usually dried up in the lower desert reaches. The river water in the lower reaches appeared just after short-term releases from the middle reaches; the groundwater level in the riparian forest region rose rapidly, but it declined again just after the short-term releases finished. Since the mixing ratio of the short-term released discharge to the groundwater in the desert-riparian fringe region was smaller than that in the riparian forest region, the short-term released discharge did not contribute to the groundwater recharge in the desert-riparian fringe region.

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow-ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter.
Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages.

http://www3.interscience.wiley.com/journal/113508995/abstract

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The impact of the timing of dust deposition on glacier runoff was evaluated using a glacier mass-balance model with a newly improved scheme to track a dusted layer in a snow layer of a glacier. The lowering of surface albedo due to the dusted layer appearing leads to a drastic increase of glacier runoff even under the same meteorological conditions. Calculations of seasonal sensitivity, the relationship between dusted date and resulting runoff, have shown that dust deposition during a melting season might cause a drastic mass outflow from a glacier through changing the surface albedo during the melting season.

http://www3.interscience.wiley.com/journal/113509005/abstract

Language：English   Publishing type：Research paper (scientific journal)  

A survey was carried out at the end moraine and the dead ice area of the Imja Glacial Lake in October 2001 and in April 2002 using a digital theodolite with a laser distance meter and differential Global Positioning System (d-GPS). The survey points covered the whole dead ice area and end moraine of the Imja Glacier, and map contours were produced at 5 m intervals. This topographical map will be a significant means to analyze the time variation of the dead ice area and end moraine in future re-mapping. Changes in the lake level and the spillway on the dead ice area since 1994 were also analyzed in comparison with the measurements in 1994 by Watanabe et al. (1995).

Language：English   Publishing type：Research paper (scientific journal)  

Meteorological observations were carried out in the Lunana region, Bhutan Himalayas, from September 2002 to October 2004. An automatic weather station (Lugge AWS) was installed at 4524 m a.s.l. on the end moraine of Lugge Glacier. In addition, air temperatures, ground temperatures and relative humidity were observed simultaneously around the AWS from late September to early October in 2003 and 2004 to investigate spatial variation of these components. Characteristics of seasonal and diurnal variations of meteorological elements are shown using the data observed by the AWS. Relatively large spatial variability of surface temperature is shown by the data observed at different sites compared to that of air temperature and relative humidity.

Authorship：Lead author   Language：English  

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Several firn/ice cores were recovered from the Siberian Altai (Belukha plateau), central Tien Shan (Inilchek glacier) and the Tibetan Plateau (Zuoqiupu glacier, Bomi) from 1998 to 2003. The comparison analyses of stable-isotope/geochemistry records obtained from these firn/ice cores identified the physical links controlling the climate-related signals at the seasonal-scale variability. The core data related to physical stratigraphy, meteorology and synoptic atmospheric dynamics were the basis for calibration, validation and clustering of the relationships between the firn-/ice-core isotope/geochemistry and snow accumulation, air temperature and precipitation origin. The mean annual accumulation (in water equivalent) was 106 g cm-2 a-1 at Inilchek glacier, 69 g cm-2 a-1 at Belukha and 196 g cm-2 a-1 at Zuoqiupu. The slopes in regression lines between the δ18O ice-core records and air temperature were found to be positive for the Tien Shan and Altai glaciers and negative for southeastern Tibet, where heavy amounts of isotopically depleted precipitation occur during summer monsoons. The technique of coupling synoptic climatology and meteorological data with δ18O and d-excess in firn-core records was developed to determine climate-related signals and to identify the origin of moisture. In Altai, two-thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation, and the rest of the precipitation was recycled over Aral-Caspian sources. In the Tien Shan, 87% of snow accumulation forms by precipitation originating from the Aral-Caspian closed basin, the eastern Mediterranean and Black Seas, and 13% from the North Atlantic.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00009

Language：English   Publishing type：Research paper (scientific journal)  

Ice-core and snow samples collected on Belukha glacier, Russian Altai mountains, were analyzed for n-alkanes by gas chromatography. On the basis of the total concentrations (T-HCs), carbon preference index (CPI) values and the plant wax contributions (WaxCn), it is suggested that mountain glaciers on the Asian continent received higher loading of n-alkanes from natural and anthropogenic sources than the Greenland ice sheet. It appears that the loading and variation of n-alkanes on glaciers in the Altai are approximately the same as those of the mountain in general, because the concentrations, CPI values and WaxCn percentages of n-alkanes in Sofiyskiy glacier, also in the Russian Altai, are at the same levels as or slightly greater than those in ice-core and snow samples from Belukha glacier. It seems that the n-alkanes on Belukha glacier are derived mainly from higher plant wax and petroleum exhaust other than from diesel engines. Vertical profiles of T-HCs and CPI values of n-alkanes show that the non-WaxCn portions and T-HCs have recently increased with a decrease in CPI values on Belukha glacier. A similar trend of n-alkanes was reported for Sofiyskiy glacier, indicating that the influence of human activities has gradually increased around the Altai.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00021

Language：English   Publishing type：Research paper (scientific journal)  

This study examines a new method for reconstructing mean summer temperature variations by using an ice core from a wet-snow zone on a summer-accumulation-type glacier. In July 2001, a 25.1 m deep ice core was recovered from the accumulation area of Sofiyskiy glacier (49°47′ N, 87°43′ E; 3435 m a.s.l.), located in the southern Chuyskiy range of the Russian Altai mountains, and a 4.5 m deep pit was excavated about 50 m northwest of the drill site. The observation site has a positive balance even during summer when melting occurs. The summer balance for each year from 1990 to 2000 was estimated from Pinaceae and Artemisia pollen peaks in these samples. Pinaceae pollen marks spring, whereas Artemisia pollen marks autumn. Moreover, meltwater intrusion did not reach the previous year's accumulation. Thus, the ice between these pollen peaks in the same year was used to estimate a summer balance. The reconstructed summer balance variations were negatively correlated with mean summer temperature variations (r = -0.72, P < 0.05). This study shows that, for summer-accumulation-type glaciers such as Sofiyskiy glacier, the most important climate factor controlling the glacier's surface mass balance is mean summer temperature. Therefore, the summer layer thickness in an ice core can be used as a proxy for reconstructing mean summer temperature variations.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00025

Language：English   Publishing type：Research paper (scientific journal)  

Though solar radiation is important for glacier mass-balance simulation, solar radiation data are not always available. As a result of analyzing meteorological data measured in the Himalaya and the Tibetan Plateau, a favorable correlation between precipitation and atmospheric transmissivity of solar radiation is found in terms of monthly values. Monthly mean solar radiation is derived from the relationship between atmospheric transmissivity of solar radiation and precipitation with input of monthly precipitation, latitude, skyline and time. The differences between estimated and observed monthly mean solar radiation are <40 W m-2 in most cases. However, the differences at some sites are significantly large. The error in the estimated solar radiation during the monsoon season can be large when the monthly mean precipitation rate is about 5 mm d^-1. Though the error in the estimated solar radiation during the non-monsoon season is generally small due to low precipitation in the Himalaya and the Tibetan Plateau during this season, it can exceed 100 W m^-2.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00052

Language：English   Publishing type：Research paper (scientific journal)  

Snow algae are cold-tolerant algae growing on snow and ice and have been reported on glaciers in many parts of the world. Blooms of snow algae can reduce the surface albedo of snow and ice and significantly affect their melting. In addition, snow algae found in ice cores can be potential indicators of the paleo-environment, making them of great interest both to the biology and the geophysics of glaciers. A snow algal community was investigated in 2002 and 2003 on Akkem glacier in the Russian Altai mountains, where no information on its biological community has previously been available. Five species of snow algae including green algae and cyanobacteria were observed on the glacier. Red snow due to a bloom of algae (Chloromonas sp.) was visually apparent in the snow area during our study periods. The total algal cell-volume biomass on the glacier ranged from 97 to 1156 μL m-2, which is equivalent to that reported previously on glaciers in the Himalaya and Alaska. The community structure showed that Mesotaenium berggrenii and/or Ancylonema nordenskioeldii, which are common species on glaciers in the Northern Hemisphere, were dominant in the ice area, while Chloromonas sp. was dominant in the snow area. Such community structures are similar to those on Alaskan and Arctic glaciers but differ from those on Himalayan and Tibetan glaciers, even though the Altai mountains are geographically closer to the Himalaya and Tibet than to Alaska. The difference in algal communities between the Altaic and other glaciers is discussed together with physical and chemical conditions affecting the algae.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00056

Language：English   Publishing type：Research paper (scientific journal)  

The albedo reduction on glacier surfaces in past summers due to microbiological activities and mineral particles should be considered to reconstruct precise fluctuation of glacier mass balance. However, there is little knowledge on preservation of the microorganisms and the mineral particles in glacier ice. In particular, influence of superimposed ice formation on these preservations is unknown. As the first step to understand the albedo reduction process and to reconstruct surface albedo changes on glaciers in northwestern China, where superimposed ice formation has an impact on glacier mass balance, we report the glacier surface level changes, seasonal and annual changes of stratigraphy and analyzed results of short ice cores at upper parts of the July 1st Glacier from 2002 to 2004. Surface melting on the glacier was accelerated by dark-colored materials composed of cryoconite and mineral particles. The glacier surface level was lowered year by year and ELA (Equilibrium Line Altitude) was much higher than that in the 1970s and 1980s. An ice core of 1.82m length included five cyanobacterial layers. As cyanobacteria grow during summer, these layers may be useful as markers for summer layers and allow to infer surface albedo changes in the past. Average annual snow mass balance estimated from the cyanobacterial peaks in the core is 313 mm, which corresponds to the annual precipitation observed near the terminus of the July 1st Glacier. These results would open up the possibilities that we could reconstruct past mass balance and albedo effects.

Language：English   Publishing type：Research paper (scientific journal)  

Hydrological observation was carried out at the July 1st Glacier in the Qilian mountains, northwest China, during the glacier melting season from 2002 to 2004. Water discharge was measured using two methods, current meter and salt water. The results of these methods showed a good correspondence. A logger for water level was settled at the glacier terminus in 2002 and at the foot of the end-moraine in 2003 and 2004. Then, variations in discharge were evaluated based on the relationship between discharge and water level. Total observed runoff depth from the basin was 834 mm in 2002. The average value of water budget components, such as precipitation, glacier mass balance, evaporation at the glacier and glacier-free area, were evaluated in 2002 from observation and meteorological data. The results indicated that the discharge from the glacier area was 6 times larger than that of the glacier-free area mainly due to glacier shrinkage.

Language：English   Publishing type：Research paper (scientific journal)  

Meteorological observations were carried out at July 1st Glacier (J1G) in Northwest China. An automatic weather station was established at the glacier terminus 4295 m a.s.l. altitude from June 2002 to August 2005. Manual meteorological observations and dust particle counting have also been conducted at the Base Camp during the summers of 2002, 2003 and 2004. The catch ratio of the precipitation was calibrated, separating it into rain and snow depending on the air temperature, which relation has been observed at Base Camp. The calibrated annual precipitation in 2002 was about 340 mm, which was more than 20% above the observed value. Inter-annual variations in the meteorological data revealed that there were remarkable wet calm and cloudy periods during the summer 2002.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Two net balance records of neighboring glaciers under different conditions are analyzed to extract temporal variations in glacier melting in the Himalayas. Significant melt was observed every year at one site (wet site), whereas no melt occurred at the second site because of its high elevation (dry site). Accumulation at the wet site of a glacier is estimated from the dry site neighboring another glacier through a measured precipitation record for a short time period. The difference between the estimated accumulation and the net balances at the wet site is obtained as the “melt index," which represents the glacier melting conditions. The melt index with an interannual timescale is significant as a climatic proxy at high elevation since no relationship between stable isotopes and temperature is established and few long-term temperature records are available at high elevations in the Himalayas. The melt index showed a decadal fluctuation with a major amplitude never reported in previous studies with respect to temperature and ice cores analyses in the Himalayas. Ice cores from a site where significant melt occurs every year have not been considered available in reconstructing past climates since climatic signals in ice were disturbed by meltwater infiltration. However, we suggest a new approach to glean temperature information by a combination of wet and dry cores, not obtainable from a good-quality ice core alone.

http://www.agu.org/pubs/crossref/2006/2005JD005894.shtml

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

In order to evaluate recent glacier shrinkage in the arid region of China, surveys using a global positioning system (GPS) and digital theodolite with laser distance meter were carried out on the July 1st glacier in the Qilian Mountains from 2002 to 2004. Benchmarks and stakes on around the glacier were installed in 2002. A new 2002 map was carefully superposed on a map created in 1975 using a salient moraine ridge and boundary of the accumulation area, since no ground control point was available in the old 1975 map. A retreat of the glacier termini has been detectable since 1956 with a notable retreat occurring between 2002 and 2003. Surface flow velocities were obtained by repeated measurements of a stake network. The new map and benchmarks provide basic information for future survey studies.

Language：English   Publishing type：Research paper (scientific journal)  

Snow algae in a shallow ice core (6.98 m long) from Yala glacier in the Langtang region of Nepal were examined for potential use as environmental markers in ice-core analysis. The ice core, taken at 5350 m a.s.l. in 1994, was estimated to contain 11 annual layers from 1984 to 1994 from the profile of algal biomass. Algal biomass in each annual layer was noted to be correlated with air temperature, and the following two environmental indices which were calculated from air temperature and precipitation at Kyangjing (3920 m a.s.l.), the village nearest to Yala glacier: estimated mean snow-cover thickness (MST) and estimated summer mass balance (SMB). Both parameters reflect snow-cover thickness on algal layers, which would be a major determinant of the light available for algal growth on the glacier. Snow algal biomass in the ice core appears to be a good environmental marker for indicating air temperature and accumulation during summer, which is important for understanding the mass balance of summer-accumulation-type glaciers in this region.

http://www.ingentaconnect.com/content/igsoc/agl/2006/00000043/00000001/art00022

Authorship：Lead author   Language：Japanese  

地球温暖化のもっとも象徴的な話題ともいえる，氷河縮小と海水準変動について，関連する研究をインベントリー，観測，モデルなどのアプローチ別に紹介し，それぞれの研究の位置づけと問題点，今後の課題を提示する．

Language：English   Publishing type：Research paper (scientific journal)  

A survey of July 1st glacier, Qilian Shan, China, was carried out in 2002. Previously, the glacier's boundary had been recorded in 1956, and further research had been carried out in the mid-1970s and 1980s. Our survey reveals that area shrinkage and surface lowering have accelerated in the past 15 years. Surface elevation changes can result from changes in accumulation, surface melting and emergence velocity. The contributions of these elements to surface lowering are evaluated at the lower part of the glacier from observations of surface velocity, ice thickness and precipitation, and from temperature data near the glacier. Apart from the effect of glacier ice redistribution, our analysis reveals quantitatively that the recent accelerated glacier shrinkage has been caused by increasing temperature. Furthermore, it is established that meltwater discharge from the glacier in the past 17 years has increased due to glacier shrinkage, by about 50% over that from 1975 to 1985.

http://www.ingentaconnect.com/content/igsoc/jog/2006/00000052/00000176/art00002

Language：English   Publishing type：Research paper (scientific journal)  

The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan–China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004.


http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VF0-4JVTBVS-1&_user=119029&_coverDate=07/31/2006&_alid=844915395&_rdoc=1&_fmt=high&_orig=search&_cdi=5996&_sort=d&_docanchor=&view=c&_ct=1&_acct=C000009318&_version=1&_urlVersion=0&_userid=119029&md5=9b8a345dbee7ce91ab9e5786e7c8139e

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

第44次南極地域観測隊ドームふじ越冬隊は2003年1月19日から2004年1月25日までドームふじ観測拠点(南緯77°19′01″,東経39°42′11″; 標高3810 m)に滞在し,雪氷・気象・宙空の観測を実施する一方,新掘削場の建設作業を実施した.この建設作業は43次隊による新掘削場の外装工事を主体した建設作業を引き継ぎ,新掘削場の内装工事を主とした.本稿では深層掘削準備作業として現地にて実施した以下の作業を記述した.ケーシングパイプ引き上げ,掘削孔拡幅,ケーシングパイプ挿入,ウインチ移設(移設用スロープの造成および10 mピット内の整備),床造成,マスト起倒用10 mピットの造成および10 mピット内の整備,ドリル作業室西側の階段造作および旧掘削場の深層ウインチ跡の床張り,机の製作,マストおよび小型門型クレーンの設置,リフター設置,ウインチ稼働テスト,チップ回収機吊り下げ用ウインチの設置,深層ウインチのケーブル巻き換え,深層ドリルの組み立ておよびマスト調整,コア貯蔵用雪洞の拡幅,コア棚の設置および一般設備工事.これらの作業に要した時間は合計で593.5日・人であり,1日平均6時間の作業時間だったので3561時・人となった.また,越冬中に実施した旧掘削場での検層準備および45次ドーム航空隊を主体とした深層掘削作業についても簡潔に記述した.

Language：English   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Reliable chronologies in ice cores and snow pits from many alpine glaciers in latitudes between 60° N and 60° S are often difficult to establish owing to problems with annual-layer counting. Problems arise from melting, wind erosion and the negligible amount of precipitation in some seasons, all of which tend to obscure the seasonal variations in δ18O and chemical concentrations that are typically used to date ice cores. However, alpine glaciers contain many species of pollen grains that peak at particular times of the year. We used the peaks in Betulaceae, Pinus, Artemisia and a combination of Abies and Picea pollen species to determine the four seasonal layers of a snow pit on Belukha glacier in Russia's Altai Mountains. Comparing the pollen-dated profiles with wind and precipitation records allows us to determine where a seasonal layer is missing. Thus, the pollen-dating method described here may be a useful tool to measure the annual snow deposition on alpine glaciers, even when some seasonal layers are eroded by wind or missing due to negligible precipitation.

http://www.ingentaconnect.com/content/igsoc/jog/2005/00000051/00000174/art00016

Language：English   Publishing type：Research paper (scientific journal)  

In the summers of 2001 and 2002, glacio-climatological research was performed at 4110-4120 m a.s.l. on the Belukha snow/firn plateau, Siberian Altai. Hundreds of samples from snow pits and a 21 m snow/firn core were collected to establish the annual/seasonal/monthly depth-accumulation scale, based on stable-isotope records, stratigraphic analyses and meteorological and synoptic data. The fluctuations of water stable-isotope records show well-preserved seasonal variations. The δ18O and δD relationships in precipitation, snow pits and the snow/firn core have the same slope to the covariance as that of the global meteoric water line. The origins of precipitation nourishing the Belukha plateau were determined based on clustering analysis of δ18O and d-excess records and examination of synoptic atmospheric patterns. Calibration and validation of the developed clusters occurred at event and monthly timescales with about 15% uncertainty. Two distinct moisture sources were shown: oceanic sources with d-excess <12‰, and the Aral-Caspian closed drainage basin sources with d-excess >12‰. Two-thirds of the annual accumulation was from oceanic precipitation, of which more than half had isotopic ratios corresponding to moisture evaporated over the Atlantic Ocean. Precipitation from the Arctic/Pacific Ocean had the lowest deuterium excess, contributing one-tenth to annual accumulation.

http://www.ingentaconnect.com/content/igsoc/jog/2005/00000051/00000175/art00013

Language：English   Publishing type：Research paper (scientific journal)  

Ice cores from temperate regions have long been expected to be useful for understanding local climate trends, but a reliable dating method has proved difficult. Here we show that measurements of pollen using samples with only 10 mL of water can give an accurate measure of the annual ice accumulation. In addition, two major types of pollen allow us to estimate the summer ice accumulation as well as the annual accumulation.

http://www.agu.org/pubs/crossref/2004/2004JF000125.shtml

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Data on the mass balance of Xiao Dongkemadi glacier in the Tanggula mountains, central Tibetan Plateau, were obtained over 5.5 years from 1989 to1995. These are the first continuous mass-balance data for a continental-type glacier on the Tibetan Plateau, where the glacier accumulates during the summer monsoon (summer-accumulation-type glacier). Mass-balance vs altitude profiles were steeper in the negative than in the positive mass-balance years. This is considered to have resulted from the effect of summer accumulation. The annual mass balance is compared with air temperature, precipitation, and black-body temperature in the area including the glacier, which is calculated from infrared radiation observations by the Japanese Geostationary Meteorological Satellite. It was found that the interannual variation in the glacier mass balance was not closely related to maximum monthly mean air temperature, while it did have a relatively good correlation with maximum monthly mean black-body temperature.

http://www.ingentaconnect.com/content/igsoc/agl/2000/00000031/00000001/art00026

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Snow algae in shallow ice cores (7 m long) from Yala Glacier in the Langtang region of Nepal were examined for potential use in ice-core dating. Ice-core samples taken at 5350 m a.s.l. in 1994 contained more than seven species of snow algae. In a vertical profile of the algal biomass, 11 distinct algal layers were observed. Seasonal observation in 1996 at the coring site indicated most algal growth occurred from late spring to late summer. Pit observation in 1991, 1992 and 1994 indicated that algal layer formation takes place annually. δ18O, chemical ions (Na+, Cl-, SO42- and NO3-) and microparticles failed to show any clear seasonal variation, particularly at depths exceeding 2 m, possibly due to heavy meltwater percolation. Snow algae in ice cores would thus appear to be accurate boundary markers of annual layers and should prove useful for ice-core dating in Himalayan-type glaciers.

http://www.ingentaconnect.com/content/igsoc/jog/2000/00000046/00000153/art00017

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The characteristics and sensitivities of a cold-based glacier on the Tibetan Plateau, where the summer monsoon provides most of the mass input to glaciers, are discussed using an energy-balance model incorporating the process of water refreezing. The model accurately represents the observational results related to the mass balance of Xiao Dongkemadi glacier on the central plateau during 1992/93. Our data revealed that the mass balance of cold glaciers cannot simply be described by the surface mass/heat balances, because about 20% of infiltrated water is refrozen and thus does not run off from the glacier. Model calculations demonstrate that glaciers in an arid environment can maintain their mass since the monsoon provides precipitation during the melting season. Snowfall in summer keeps surface albedo high and largely restrains ablation. Nevertheless, the calculations also make clear that glaciers on the plateau are more vulnerable than those of other regions because of summer accumulation. In the monsoon climate, warming would cause not only a decrease in accumulation, but also a drastic increase in ablation in combination with surface-albedo lowering. Therefore, although glaciers on and around the plateau can be sustained by summer accumulation, they are more vulnerable to warming than winter-accumulation-type glaciers.

http://www.ingentaconnect.com/content/igsoc/jog/2000/00000046/00000153/art00009

Authorship：Lead author   Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：Japanese  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Meeting report  

CiNii Books

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

Event date： 2024.9

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Venue：幕張 & online   Country：Japan  

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Venue：幕張 & online   Country：Japan  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Venue：幕張 & online   Country：Japan  

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Event date： 2021.9

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Language：English   Presentation type：Oral presentation (general)  

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Event date： 2021.5 - 2021.6

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Event date： 2021.5 - 2021.6

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Event date： 2021

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Event date： 2021

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Event date： 2020.12

Language：English   Presentation type：Poster presentation  

Venue：Online   Country：United States  

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Country：Japan  

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Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.7

Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

Venue：Online  

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Language：English   Presentation type：Oral presentation (general)  

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Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco, USA   Country：United States  

Event date： 2019.12

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Venue：San Francisco, USA   Country：United States  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco, USA   Country：United States  

Event date： 2019.12

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Venue：San Francisco, USA   Country：United States  

Event date： 2019.12

Language：English   Presentation type：Poster presentation  

Venue：San Francisco, USA   Country：United States