Faculty Profiles - FUJITA, Koji

High-resolution analyses of concentrations and sizes of refractory black carbon particles deposited in northwestern Greenland over the past 350 years – Part 2: Seasonal and temporal trends in refractory black carbon originated from fossil fuel combustion and biomass burning Reviewed International coauthorship

Kumiko Goto-Azuma, Yoshimi Ogawa-Tsukagawa, Kaori Fukuda, Koji Fujita, Motohiro Hirabayashi, Remi Dallmayr, Jun Ogata, Nobuhiro Moteki, Tatsuhiro Mori, Sho Ohata, Yutaka Kondo, Makoto Koike, Sumito Matoba, Moe Kadota, Akane Tsushima, Naoko Nagatsuka, Teruo Aoki

Atmospheric Chemistry and Physics Vol. 25 ( 1 ) page： 657 - 683 2025.1

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

Abstract. The roles and impacts of refractory black carbon (rBC), an important aerosol species affecting Earth's radiation budget, are not well understood owing to a lack of accurate long-term observations. To study the temporal changes in rBC since the pre-industrial period, we analyzed rBC in an ice core drilled in northwestern Greenland. Using an improved technique for rBC measurement and a continuous flow analysis (CFA) system, we obtained accurate and high-temporal-resolution records of rBC particle size and mass/number concentrations for the past 350 years. Number and mass concentrations, which both started to increase in the 1870s associated with the inflow of anthropogenically derived rBC, reached their maxima in the 1910s–1920s and then subsequently decreased. Backward-trajectory analyses suggest that North America was likely the dominant source region of the anthropogenic rBC in the ice core. The increase in anthropogenic rBC shifted the annual concentration peaks of rBC from summer to winter–early spring. After rBC concentrations diminished to pre-industrial levels, the annual peak concentration of rBC returned to the summer. We found that anthropogenic rBC particles were larger than biomass burning rBC particles. By separating the rBC in winter and summer, we reconstructed the temporal variations in rBC that originated from biomass burning, including the period with large anthropogenic input. The rBC that originated from biomass burning showed no trend in increase until the early 2000s. Finally, possible albedo reductions due to rBC are discussed. Our new data provide key information for validating aerosol and climate models, thereby supporting improved projections of future climate and environment.

DOI： 10.5194/acp-25-657-2025

Technical note: High-resolution analyses of concentrations and sizes of refractory black carbon particles deposited in northwestern Greenland over the past 350 years – Part 1: Continuous flow analysis of the SIGMA-D ice core using the wide-range Single-Particle Soot Photometer and a high-efficiency nebulizer Reviewed International coauthorship

Kumiko Goto-Azuma, Remi Dallmayr, Yoshimi Ogawa-Tsukagawa, Nobuhiro Moteki, Tatsuhiro Mori, Sho Ohata, Yutaka Kondo, Makoto Koike, Motohiro Hirabayashi, Jun Ogata, Kyotaro Kitamura, Kenji Kawamura, Koji Fujita, Sumito Matoba, Naoko Nagatsuka, Akane Tsushima, Kaori Fukuda, Teruo Aoki

Atmospheric Chemistry and Physics Vol. 24 ( 22 ) page： 12985 - 13000 2024.11

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

Abstract. Ice cores can provide long-term records of refractory black carbon (rBC), an important aerosol species closely linked to the climate and environment. However, previous studies of ice cores only analyzed rBC particles with a diameter of < 500 nm, which could have led to an underestimation of rBC mass concentrations. Information on the size distribution of rBC particles is very limited, and there are no Arctic ice core records of the temporal variation in rBC size distribution. In this study, we applied a recently developed improved technique to analyze the rBC concentration in an ice core drilled at the SIGMA-D site in northwestern Greenland. The improved technique, which uses the modified Single-Particle Soot Photometer (SP2) and a high-efficiency nebulizer, widens the measurable range of rBC particle size. For high-resolution continuous analyses of ice cores, we developed a continuous flow analysis (CFA) system. Coupling of the improved rBC measurement technique with the CFA system allows accurate high-resolution measurements of the size distribution and concentration of rBC particles with a diameter between 70 nm and 4 µm, with minimal particle losses. Using this technique, we reconstructed the size distributions and the number and mass concentrations of rBC particles during the past 350 years. On the basis of the size distributions, we assessed the underestimation of rBC mass concentrations measured using the conventional SP2s. For the period 2003–2013, the underestimation of the average mass concentration would have been 12 %–31 % for the SIGMA-D core.

DOI： 10.5194/acp-24-12985-2024

Quality Assessment of Multiple UAV-SfM DEMs Derived for Impact Assessment of a Co-Seismic Avalanche in the Himalayas Reviewed International coauthorship

Sojiro Sunako, Koji Fujita, Satoru Yamaguchi, Hiroshi Inoue, Walter W. Immerzeel, Takeki Izumi, Rijan B. Kayastha

Journal of Disaster Research Vol. 19 ( 5 ) page： 865 - 873 2024.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Fuji Technology Press Ltd.

Combined with the structure from motion (SfM) technique, unmanned aerial vehicles (UAVs) are powerful tools for generating high-resolution digital elevation models (DEMs) for application in hazard assessments. During our field observations in October 2015 at Langtang Village, which was destroyed by the Gorkha earthquake in April 2015, three different UAVs with mounted cameras were operated to evaluate the volume of the avalanche deposit covering the village. This study evaluated the performance of DEMs created from the different cameras on board those UAVs. Multiple DEMs for the different cameras, including Sony-α7R (PA7), Ricoh-GR (XGR), and Canon-IXUS (EIX), were created using SfM software. All DEMs were compared with a base DEM created from differential global positioning system survey data, which was obtained simultaneously with the UAV campaigns. The results show that the elevation difference of PA7-, XGR-, and EIX-DEMs are within ±0.14 m; the standard deviations of elevation difference range from 0.33 to 0.40 m. Although there were slightly larger differences in elevation on the southwest-to-west sides of the XGR- and EIX-DEMs, which can be attributed mainly to the flight paths and ground control point network, our DEMs are still of high enough quality to be used in hazard assessments.

DOI： 10.20965/jdr.2024.p0865

Long-term relationships between summer clouds and aerosols over mid-high latitudes of the Northern Hemisphere Reviewed

Akihisa Watari, Yoshinori Iizuka, Koji Fujita, Hirohiko Masunaga, Kazuaki Kawamoto

Scientific Reports Vol. 14 ( 1 ) page： 9059 2024.4

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

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

Modelling runoff components and hydrological processes in glaciated catchments of the inner Tien-Shan, Kyrgyzstan Reviewed International coauthorship

Sanjar Sadyrov, Kenji Tanaka, Rysbek Satylkanov, Temur Khujanazarov, Yoshiya Touge, Koji Fujita

Frontiers in Earth Science Vol. 11 page： 1306476 2024.4

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

Anthropogenic Influence on Tropospheric Reactive Bromine Since the Pre‐industrial: Implications for Arctic Ice‐Core Bromine Trends Reviewed International coauthorship

Shuting Zhai, Joseph R. McConnell, Nathan Chellman, Michel Legrand, Thomas Opel, Hanno Meyer, Lyatt Jaeglé, Kaitlyn Confer, Koji Fujita, Xuan Wang, Becky Alexander

Geophysical Research Letters Vol. 51 ( 5 ) page： e2023GL107733 2024.3

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

Abstract

Tropospheric reactive bromine (Bry) influences the oxidation capacity of the atmosphere by acting as a sink for ozone and nitrogen oxides. Aerosol acidity plays a crucial role in Bry 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 Bry changes, consistent with the observed relationship between acidity and bromine. The influence of atmospheric acidity on Bry should be considered in interpretation of ice‐core bromine trends.

DOI： 10.1029/2023GL107733

Foehn winds influence surface ablation on Glaciar Perito Moreno, Southern Patagonian Icefield Reviewed International coauthorship

Masahiro Minowa, Pedro Skvarca, Koji Fujita

Journal of Glaciology Vol. 70 page： e40 2024.1

Major metallic elements (Al, Ca, and Fe) and size distribution of mineral particles in recent snow in inland Northeast Greenland Reviewed International coauthorship

Yuki KOMURO, Fumio NAKAZAWA, Kumiko GOTO-AZUMA, Motohiro HIRABAYASHI, Wataru SHIGEYAMA, Koji FUJITA, Jørgen Peder STEFFENSEN, Dorthe DAHL-JENSEN

Bulletin of Glaciological Research Vol. 42 page： 49 - 60 2024

Quality-controlled meteorological datasets from SIGMA automatic weather stations in northwest Greenland, 2012–2020 Reviewed International journal

Motoshi Nishimura, Teruo Aoki, Masashi Niwano, Sumito Matoba, Tomonori Tanikawa, Tetsuhide Yamasaki, Satoru Yamaguchi, Koji Fujita

Earth System Science Data Vol. 15 ( 11 ) page： 5207 - 5226 2023.11

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

Implications of Snowpack Reactive Bromine Production for Arctic Ice Core Bromine Preservation Reviewed International coauthorship

Shuting Zhai, William Swanson, Joseph R. McConnell, Nathan Chellman, Thomas Opel, Michael Sigl, Hanno Meyer, Xuan Wang, Lyatt Jaeglé, Jochen Stutz, Jack E. Dibb, Koji Fujita, Becky Alexander

Journal of Geophysical Research: Atmospheres Vol. 128 ( 20 ) page： e2023JD039257 2023.10

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

SE‐Dome II Ice Core Dating With Half‐Year Precision: Increasing Melting Events From 1799 to 2020 in Southeastern Greenland Reviewed

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

Kaoru Kawakami, Yoshinori Iizuka, Mahiro Sasage, Mai Matsumoto, Takeshi Saito, Akira Hori, Sakiko Ishino, Shuji Fujita, Koji Fujita, Keita Takasugi, Takumi Hatakeyama, Saaya Hamamoto, Akihisa Watari, Nao Esashi, Miu Otsuka, Ryu Uemura, Kazuho Horiuchi, Masahiro Minowa, Shohei Hattori, Teruo Aoki, Motohiro Hirabayashi, Kenji Kawamura, Sumito Matoba

Journal of Geophysical Research: Atmospheres Vol. 128 ( 20 ) page： e2023JD038874 2023.10

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

Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment Reviewed International coauthorship

Pascal Buri, Simone Fatichi, Thomas E. Shaw, Evan S. Miles, Michael J. McCarthy, Catriona L. Fyffe, Stefan Fugger, Shaoting Ren, Marin Kneib, Achille Jouberton, Jakob Steiner, Koji Fujita, Francesca Pellicciotti

Water Resources Research Vol. 59 ( 10 ) page： e2022WR033841 2023.10

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

Modelling the development and decay of cryoconite holes in northwestern Greenland Reviewed

Yukihiko Onuma, Koji Fujita, Nozomu Takeuchi, Masashi Niwano, Teruo Aoki

The Cryosphere Vol. 17 ( 8 ) page： 3309 - 3328 2023.8

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

A long-term mass-balance reconstruction (1974–2021) and a decadal in situ mass-balance record (2011–2021) of Rikha Samba Glacier, central Himalaya Reviewed International coauthorship

Tika Ram Gurung, Rijan Bhakta Kayastha, Koji Fujita, Sharad Prasad Joshi, Anna Sinisalo, James D. Kirkham

Journal of Glaciology Vol. 69 ( 276 ) page： 723 - 736 2023.8

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

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

AsiaPEX: Challenges and Prospects in Asian Precipitation Research Reviewed International coauthorship

Toru Terao, Shinjiro Kanae, Hatsuki Fujinami, Someshwar Das, A. P. Dimri, Subashisa Dutta, Koji Fujita, Azusa Fukushima, Kyung-Ja Ha, Masafumi Hirose, Jinkyu Hong, Hideyuki Kamimera, Rijan Bhakta Kayastha, Masashi Kiguchi, Kazuyoshi Kikuchi, Hyun Mee Kim, Akio Kitoh, Hisayuki Kubota, Weiquang Ma, Yaoming Ma, Millind Mujumdar, Masato I. Nodzu, Tomonori Sato, Z. Su, Shiori Sugimoto, Hiroshi G. Takahashi, Yuhei Takaya, Shuyu Wang, Kun Yang, Satoru Yokoi, Jun Matsumoto

Bulletin of the American Meteorological Society Vol. 104 ( 4 ) page： E884 - E908 2023.4

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

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

Up-glacier propagation of surface lowering of Yala Glacier, Langtang Valley, Nepal Himalaya Reviewed International coauthorship

Sojiro Sunako, Koji Fujita, Takeki Izumi, Satoru Yamaguchi, Akiko Sakai, Rijan Bhakta Kayastha

Journal of Glaciology Vol. 69 ( 274 ) page： 425 - 432 2023.4

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

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

Multiscale Processes Leading to Heavy Precipitation in the Eastern Nepal Himalayas Reviewed International coauthorship

Hidetaka Hirata, Hatsuki Fujinami, Hironari Kanamori, Yota Sato, Masaya Kato, Rijan B. Kayastha, Madan L. Shrestha, Koji Fujita

Journal of Hydrometeorology Vol. 24 ( 4 ) page： 641 - 658 2023.4

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

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

Evolution of snow algae, from cosmopolitans to endemics, revealed by DNA analysis of ancient ice Reviewed International coauthorship International journal

Takahiro Segawa, Takahiro Yonezawa, Ryo Matsuzaki, Hiroshi Mori, Ayumi Akiyoshi, Francisco Navarro, Koji Fujita, Vladimir B. Aizen, Zhongqin Li, Shuhei Mano, Nozomu Takeuchi

The ISME Journal Vol. 17 ( 4 ) page： 491 - 501 2023.4

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

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

A WIGGLE-MATCHED 297-YR TREE-RING OXYGEN ISOTOPE RECORD FROM THAILAND: INVESTIGATING THE 14C OFFSET INDUCED BY AIR MASS TRANSPORT FROM THE INDIAN OCEAN Reviewed International coauthorship

Masaki Sano, Nathsuda Pumijumnong, Koji Fujita, Masataka Hakozaki, Fusa Miyake, Takeshi Nakatsuka

Radiocarbon Vol. 65 ( 2 ) page： 505 - 519 2023.4

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

Climate and Surface Mass Balance at Glaciar Perito Moreno, Southern Patagonia Reviewed International coauthorship

Masahiro Minowa, Pedro Skvarca, Koji Fujita

Journal of Climate Vol. 36 ( 2 ) page： 625 - 641 2023.1

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

Increased oceanic dimethyl sulfide emissions in areas of sea ice retreat inferred from a Greenland ice core Reviewed

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

Yutaka Kurosaki, Sumito Matoba, Yoshinori Iizuka, Koji Fujita, Rigen Shimada

Communications Earth & Environment Vol. 3 ( 1 ) page： 327 2022.12

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

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

Multi-decadal monsoon characteristics and glacier response in High Mountain Asia Reviewed International coauthorship

T E Shaw, E S Miles, D Chen, A Jouberton, M Kneib, S Fugger, T Ou, H-W Lai, K Fujita, W Yang, S Fatichi, F Pellicciotti

Environmental Research Letters Vol. 17 ( 10 ) page： 104001 - 104001 2022.10

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

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

Editorial: Debris-covered glaciers: Formation, governing processes, present status and future directions Invited International coauthorship

Shukla Aparna, Nicholson Lindsey, Banerjee Argha, Fujita Koji, Quincey Duncan J.

Frontiers in Earth Science Vol. 10 2022.9

Land- to lake-terminating transition triggers dynamic thinning of a Bhutanese glacier Reviewed International coauthorship

Yota Sato, Koji Fujita, Hiroshi Inoue, Akiko Sakai, Karma

The Cryosphere Vol. 16 ( 6 ) page： 2643 - 2654 2022.7

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

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

Mass Balance of Four Mongolian Glaciers: In-situ Measurements, Long-Term Reconstruction and Sensitivity Analysis Reviewed International coauthorship International journal

Purevdagva Khalzan, Akiko Sakai, Koji Fujita

Frontiers in Earth Science Vol. 9 page： 785306 2022.1

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

Soluble salts in deserts as a source of sulfate aerosols in an Antarctic ice core during the last glacial period Reviewed International journal

Ryu Uemura, Kosuke Masaka, Yoshinori Iizuka, Motohiro Hirabayashi, Hitoshi Matsui, Risei Matsumoto, Miki Uemura, Koji Fujita, Hideaki Motoyama

Earth and Planetary Science Letters Vol. 578 page： 117299 - 117299 2022.1

Ice core drilling on a high-elevation accumulation zone of Trambau Glacier in the Nepal Himalaya Reviewed International coauthorship International journal

Akane Tsushima, Morihiro Miyahara, Tetsuhide Yamasaki, Nao Esashi, Yota Sato, Rijan B. Kayastha, Ang J. B. Lama Sherpa, Masaki Sano, Koji Fujita

Annals of Glaciology Vol. 62 ( 85-86 ) page： 353 - 359 2021.9

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

Anthropogenic Impacts on Tropospheric Reactive Chlorine Since the Preindustrial Reviewed International coauthorship International journal

Shuting Zhai, Xuan Wang, Joseph R. McConnell, Lei Geng, Jihong Cole‐Dai, Michael Sigl, Nathan Chellman, Tomás Sherwen, Ryan Pound, Koji Fujita, Shohei Hattori, Jonathan M. Moch, Lei Zhu, Mat Evans, Michel Legrand, Pengfei Liu, Daniel Pasteris, Yuk‐Chun Chan, Lee T. Murray, Becky Alexander

Geophysical Research Letters Vol. 48 ( 14 ) page： e2021GL093808 2021.7

Twice‐Daily Monsoon Precipitation Maxima in the Himalayas Driven by Land Surface Effects Reviewed International coauthorship International journal

Hatsuki Fujinami, Koji Fujita, Nobuhiro Takahashi, Tomonori Sato, Hironari Kanamori, Sojiro Sunako, Rijan B. Kayastha

Journal of Geophysical Research: Atmospheres Vol. 126 ( 13 ) 2021.7

Physically Based Summer Temperature Reconstruction From Melt Layers in Ice Cores Reviewed International journal Open Access

Koji Fujita, Sumito Matoba, Yoshinori Iizuka, Nozomu Takeuchi, Akane Tsushima, Yutaka Kurosaki, Teruo Aoki

Earth and Space Science Vol. 8 ( 7 ) 2021.7

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

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

Variations in mineralogy of dust in an ice core obtained from northwestern Greenland over the past 100 years Reviewed International coauthorship International journal Open Access

Naoko Nagatsuka, Kumiko Goto-Azuma, Akane Tsushima, Koji Fujita, Sumito Matoba, Yukihiko Onuma, Remi Dallmayr, Moe Kadota, Motohiro Hirabayashi, Jun Ogata, Yoshimi Ogawa-Tsukagawa, Kyotaro Kitamura, Masahiro Minowa, Yuki Komuro, Hideaki Motoyama, Teruo Aoki

Climate of the Past Vol. 17 ( 3 ) page： 1341 - 1362 2021.6

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

Ice Cliff Dynamics of Debris-Covered Trakarding Glacier in the Rolwaling Region, Nepal Himalaya Reviewed International coauthorship International journal Open Access

Yota Sato, Koji Fujita, Hiroshi Inoue, Sojiro Sunako, Akiko Sakai, Akane Tsushima, Evgeny A. Podolskiy, Rakesh Kayastha, Rijan B. Kayastha

Frontiers in Earth Science Vol. 9 2021.6

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 (&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

Projected land ice contributions to twenty-first-century sea level rise Reviewed International coauthorship International journal

Tamsin L. Edwards, Sophie Nowicki, Ben Marzeion, Regine Hock, Heiko Goelzer, Hélène Seroussi, Nicolas C. Jourdain, Donald A. Slater, Fiona E. Turner, Christopher J. Smith, Christine M. McKenna, Erika Simon, Ayako Abe-Ouchi, Jonathan M. Gregory, Eric Larour, William H. Lipscomb, Antony J. Payne, Andrew Shepherd, Cécile Agosta, Patrick Alexander, Torsten Albrecht, Brian Anderson, Xylar Asay-Davis, Andy Aschwanden, Alice Barthel, Andrew Bliss, Reinhard Calov, Christopher Chambers, Nicolas Champollion, Youngmin Choi, Richard Cullather, Joshua Cuzzone, Christophe Dumas, Denis Felikson, Xavier Fettweis, Koji Fujita, Benjamin K. Galton-Fenzi, Rupert Gladstone, Nicholas R. Golledge, Ralf Greve, Tore Hattermann, Matthew J. Hoffman, Angelika Humbert, Matthias Huss, Philippe Huybrechts, Walter Immerzeel, Thomas Kleiner, Philip Kraaijenbrink, Sébastien Le clec’h, Victoria Lee, Gunter R. Leguy, Christopher M. Little, Daniel P. Lowry, Jan-Hendrik Malles, Daniel F. Martin, Fabien Maussion, Mathieu Morlighem, James F. O’Neill, Isabel Nias, Frank Pattyn, Tyler Pelle, Stephen F. Price, Aurélien Quiquet, Valentina Radić, Ronja Reese, David R. Rounce, Martin Rückamp, Akiko Sakai, Courtney Shafer, Nicole-Jeanne Schlegel, Sarah Shannon, Robin S. Smith, Fiammetta Straneo, Sainan Sun, Lev Tarasov, Luke D. Trusel, Jonas Van Breedam, Roderik van de Wal, Michiel van den Broeke, Ricarda Winkelmann, Harry Zekollari, Chen Zhao, Tong Zhang, Thomas Zwinger

Nature Vol. 593 ( 7857 ) page： 74 - + 2021.5

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

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

Isotopic evidence for acidity-driven enhancement of sulfate formation after SO2 emission control Reviewed International coauthorship International journal Open Access

Shohei Hattori, Yoshinori Iizuka, Becky Alexander, Sakiko Ishino, Koji Fujita, Shuting Zhai, Tomás Sherwen, Naga Oshima, Ryu Uemura, Akinori Yamada, Nozomi Suzuki, Sumito Matoba, Asuka Tsuruta, Joel Savarino, Naohiro Yoshida

Science Advances Vol. 7 ( 19 ) page： eabd4610 - eabd4610 2021.5

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

Ice Core Drilling and the Related Observations at SE-Dome site, southeastern Greenland Ice Sheet Reviewed

SIGMAと関連プロジェクトによるグリーンランド氷床上の大気・雪氷・雪氷微生物研究 - ArCS IIプロジェクトへのつながり -. Reviewed

青木輝夫, 的場澄人, 庭野匡思, 朽木勝幸, 谷川朋範, 竹内望, 山口悟, 本山秀明, 藤田耕史, 山崎哲秀, 飯塚芳徳, 堀雅裕, 島田利元, 植竹淳, 永塚尚子, 大沼友貴彦, 橋本明弘, 石元裕史, 田中泰宙, 大島長, 梶野瑞王, 足立光司, 黒﨑豊, 杉山慎, 津滝俊, 東久美子, 八久保晶弘, 川上薫, 木名瀨健

雪氷 Vol. 83 ( 2 ) page： 169 - 191 2021.3

Increasing dust emission from ice free terrain in southeastern Greenland since 2000 Reviewed International journal

Tomomi Amino, Yoshinori Iizuka, Sumito Matoba, Rigen Shimada, Naga Oshima, Toshitaka Suzuki, Takuto Ando, Teruo Aoki, Koji Fujita

Polar Science Vol. 27 page： 100599 - 100599 2021.3

雪氷 : journal of the Japanese Society of Snow and Ice Vol. 83 ( 2 ) page： 169 - 191 2021.3

氷床表面質量収支の実態とそのモデリングの試み：2020年夏最新版. Reviewed

庭野匡思, 青木輝夫, 橋本明弘, 大島長, 梶野瑞王, 大沼友貴彦, 藤田耕史, 山口悟, 島田利元, 竹内望, 津滝俊, 本山秀明, 石井正好, 杉山慎, 平沢尚彦, 阿部彩子

雪氷 Vol. 83 ( 1 ) page： 27 - 50 2021.1

Review of the current polar ice sheet surface mass balance and its modelling: the 2020 summer edition

庭野匡思, 青木輝夫, 青木輝夫, 橋本明弘, 大島長, 梶野瑞王, 大沼友貴彦, 藤田耕史, 山口悟, 島田利元, 竹内望, 津滝俊, 津滝俊, 本山秀明, 石井正好, 杉山慎, 平沢尚彦, 阿部彩子, 阿部彩子

雪氷 Vol. 83 ( 1 ) 2021

Yoshinori IIZUKA, Sumito MATOBA, Masahiro MINOWA, Tetsuhide YAMASAKI, Kaoru KAWAKAMI, Ayako KAKUGO, Morihiro MIYAHARA, Akihiro HASHIMOTO, Masashi NIWANO, Tomonori TANIKAWA, Koji FUJITA, Teruo AOKI

Bulletin of Glaciological Research Vol. 39 page： 1 - 12 2021

The Second Deep Ice Coring at Dome Fuji, Antarctica Reviewed International coauthorship

Antarctic Record Vol. 64 ( 64 ) page： 284 - 329 2020.12

GrSMBMIP: intercomparison of the modelled 1980–2012 surface mass balance over the Greenland Ice Sheet Reviewed International coauthorship International journal

Xavier Fettweis, Stefan Hofer, Uta Krebs-Kanzow, Charles Amory, Teruo Aoki, Constantijn J. Berends, Andreas Born, Jason E. Box, Alison Delhasse, Koji Fujita, Paul Gierz, Heiko Goelzer, Edward Hanna, Akihiro Hashimoto, Philippe Huybrechts, Marie-Luise Kapsch, Michalea D. King, Christoph Kittel, Charlotte Lang, Peter L. Langen, Jan T. M. Lenaerts, Glen E. Liston, Gerrit Lohmann, Sebastian H. Mernild, Uwe Mikolajewicz, Kameswarrao Modali, Ruth H. Mottram, Masashi Niwano, Brice Noël, Jonathan C. Ryan, Amy Smith, Jan Streffing, Marco Tedesco, Willem Jan van de Berg, Michiel van den Broeke, Roderik S. W. van de Wal, Leo van Kampenhout, David Wilton, Bert Wouters, Florian Ziemen, Tobias Zolles

The Cryosphere Vol. 14 ( 11 ) page： 3935 - 3958 2020.11

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

Partitioning the Uncertainty of Ensemble Projections of Global Glacier Mass Change Reviewed International coauthorship International journal

Ben Marzeion, Regine Hock, Brian Anderson, Andrew Bliss, Nicolas Champollion, Koji Fujita, Matthias Huss, Walter W. Immerzeel, Philip Kraaijenbrink, Jan‐Hendrik Malles, Fabien Maussion, Valentina Radić, David R. Rounce, Akiko Sakai, Sarah Shannon, Roderik Wal, Harry Zekollari

Earth's Future Vol. 8 ( 7 ) page： e2019EF001470 2020.7

The influence of water percolation through crevasses on the thermal regime of a Himalayan mountain glacier Reviewed International coauthorship International journal

Adrien Gilbert, Anna Sinisalo, Tika R. Gurung, Koji Fujita, Sudan B. Maharjan, Tenzing C. Sherpa, Takehiro Fukuda

The Cryosphere Vol. 14 ( 4 ) page： 1273 - 1288 2020.4

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

Contrasting thinning patterns between lake- and land-terminating glaciers in the Bhutanese Himalaya Reviewed International coauthorship International journal Open Access

Tsutaki, Shun, Fujita, Koji, Nuimura, Takayuki, Sakai, Akiko, Sugiyama, Shin, Komori, Jiro, Tshering, Phuntsho

CRYOSPHERE Vol. 13 ( 10 ) page： 2733 - 2750 2019.10

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

Mass balance of Trambau Glacier, Rolwaling region, Nepal Himalaya: in-situ observations, long-term reconstruction and mass-balance sensitivity Reviewed International coauthorship International journal Open Access

Sunako, Sojiro, Fujita, Koji, Sakai, Akiko, Kayastha, Rijan B.

JOURNAL OF GLACIOLOGY Vol. 65 ( 252 ) page： 605 - 616 2019.8

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

Reduced marine phytoplankton sulphur emissions in the Southern Ocean during the past seven glacials Reviewed International journal Open Access

Goto-Azuma K, Hirabayashi M, Motoyama H, Miyake T, Kuramoto T, Uemura R, Igarashi M, Iizuka Y, Sakurai T, Horikawa S, Suzuki K, Suzuki T, Fujita K, Kondo Y, Hattori S, Fujii Y

Nature Communications Vol. 10 ( 1 ) page： 324 2019.7

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

Influence of summer sublimation on δD, δ18O and δ17O in precipitation, East Antarctica, and implications for climate reconstruction from ice cores Reviewed International coauthorship International journal

Pang HX, Hou SG, Landais A, Masson-Delmotte V, Jouzel J, Steen-Larsen HC, Risi C, Zhang WB, Wu SY, Li YS, An CL, Wang YT, Prie F, Minster B, Falourd S, Stenni B, Scarchilli C, Fujita K, Grigioni P

Journal of Geophysical Research: Atmospheres Vol. 124 ( 13 ) page： 7339 - 7358 2019.7

Viscoelastic modeling of nocturnal thermal fracturing in a Himalayan debris-covered glacier Reviewed International coauthorship International journal

Podolskiy EA, Fujita K, Sunako S, Sato Y

Journal of Geophysical Research: Earth Surface Vol. 124 ( 6 ) page： 1485 - 1515 2019.6

Simulations of black carbon (BC) aerosol impact over Hindu Kush Himalayan sites: validation, sources, and implications on glacier runoff Reviewed International coauthorship

Santra S, Verma S, Fujita K, Chakraborty I, Boucher O, Takemura T, Burkhart JF, Matt F, Sharma M

Atmospheric Chemistry and Physics Vol. 19 ( 4 ) page： 2441 - 2460 2019.2

Assessment for paleoclimatic utility of biomass burning tracers in SE-Dome ice core, Greenland Reviewed International coauthorship Open Access

Fahmida Parvin, Osamu Seki, Koji Fujita, Yoshinori Iizuka, Sumito Matoba, Takuto Ando, Ken Sawada

Atmospheric Environment Vol. 196 page： 86 - 94 2019.1

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

Annual layer counting using pollen grains of the Grigoriev ice core from the Tien Shan Mountains, central Asia Reviewed International coauthorship International journal Open Access

Takeuchi N, Sera S, Fujita K, Aizen VB, Kubota J

Arctic, Antarctic, and Alpine Research Vol. 51 ( 1 ) page： 299 - 312 2019

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

Status and Change of the Cryosphere in the Extended Hindu Kush Himalaya Region Invited Reviewed International coauthorship

Bolch Tobias, Shea Joseph M., Liu Shiyin, Azam Farooq M., Gao Yang, Gruber Stephan, Immerzeel Walter W., Kulkarni Anil, Li Huilin, Tahir Adnan A., Zhang Guoqing, Zhang Yinsheng, Bannerjee Argha, Berthier Etienne, Brun Fanny, Kaab Andreas, Kraaijenbrink Phillip, Moholdt Geir, Nicholson Lindsey, Pepin Nicholas, Racoviteanu Adina, Fujita Koji

HINDU KUSH HIMALAYA ASSESSMENT: MOUNTAINS, CLIMATE CHANGE, SUSTAINABILITY AND PEOPLE page： 209 - 255 2019

Nocturnal thermal fracturing of a Himalayan debris-covered glacier revealed by ambient seismic noise Reviewed International coauthorship

Podolskiy EA, Fujita K, Sunako S, Tsushima A, Kayastha RB

Geophysical Research Letters Vol. 45 ( 18 ) page： 9699 - 9709 2018.9

Demographic analysis of cyanobacteria based on the mutation rates estimated from an ancient ice core Reviewed International coauthorship Open Access

Takahiro Segawa, Nozomu Takeuchi, Koji Fujita, Vladimir B. Aizen, Eske Willerslev, Takahiro Yonezawa

Heredity Vol. 120 ( 6 ) page： 562 - 573 2018.6

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

Use of Water Balance and Tracer-Based Approaches to Monitor Groundwater Recharge in the Hyper-Arid Gobi Desert of Northwestern China Reviewed International coauthorship

Akiyama T, Kubota J, Fujita K, Tsujimura M, Nakawo M, Avtar R, Kharrazi A

Environments Vol. 5 ( 5 ) page： 55 - 15 2018.5

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

Asynchrony between Antarctic temperature and CO2 associated with obliquity over the past 720,000 years Reviewed International coauthorship Open Access

Ryu Uemura, Hideaki Motoyama, Valérie Masson-Delmotte, Jean Jouzel, Kenji Kawamura, Kumiko Goto-Azuma, Shuji Fujita, Takayuki Kuramoto, Motohiro Hirabayashi, Takayuki Miyake, Hiroshi Ohno, Koji Fujita, Ayako Abe-Ouchi, Yoshinori Iizuka, Shinichiro Horikawa, Makoto Igarashi, Keisuke Suzuki, Toshitaka Suzuki, Yoshiyuki Fujii

Nature Communications Vol. 9 ( 1 ) page： 961 2018.3

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

NHM-SMAP: Spatially and temporally high-resolution nonhydrostatic atmospheric model coupled with detailed snow process model for Greenland Ice Sheet Reviewed Open Access

Masashi Niwano, Teruo Aoki, Akihiro Hashimoto, Sumito Matoba, Satoru Yamaguchi, Tomonori Tanikawa, Koji Fujita, Akane Tsushima, Yoshinori Iizuka, Rigen Shimada, Masahiro Hori

Cryosphere Vol. 12 ( 2 ) page： 635 - 655 2018.2

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

Review of the status and mass changes of Himalayan-Karakoram glaciers Reviewed International coauthorship Open Access

Mohd Farooq Azam, Patrick Wagnon, Etienne Berthier, Christian Vincent, Koji Fujita, Jeffrey S. Kargel

Journal of Glaciology Vol. 64 ( 243 ) page： 61 - 74 2018.2

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

A 60 Year Record of Atmospheric Aerosol Depositions Preserved in a High-Accumulation Dome Ice Core, Southeast Greenland Reviewed Open Access

Yoshinori Iizuka, Ryu Uemura, Koji Fujita, Shohei Hattori, Osamu Seki, Chihiro Miyamoto, Toshitaka Suzuki, Naohiro Yoshida, Hideaki Motoyama, Sumito Matoba

Journal of Geophysical Research: Atmospheres Vol. 123 ( 1 ) page： 574 - 589 2018.1

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

Surface lowering of the debris-covered area of Kanchenjunga Glacier in the eastern Nepal Himalaya since 1975, as revealed by Hexagon KH-9 and ALOS satellite observations Reviewed Open Access

Damodar Lamsal, Koji Fujita, Akiko Sakai

CRYOSPHERE Vol. 11 ( 6 ) page： 2815 - 2827 2017.12

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

Seasonal-Scale Dating of a Shallow Ice Core From Greenland Using Oxygen Isotope Matching Between Data and Simulation Reviewed Open Access

Ryoto Furukawa, Ryu Uemura, Koji Fujita, Jesper Sjolte, Kei Yoshimura, Sumito Matoba, Yoshinori Iizuka

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 122 ( 20 ) page： 10873 - 10887 2017.10

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

Contrasting glacier responses to recent climate change in high-mountain Asia Reviewed Open Access

Akiko Sakai, Koji Fujita

SCIENTIFIC REPORTS Vol. 7 ( 1 ) page： 13717 2017.10

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

Downwasting of the debris-covered area of Lirung Glacier in Langtang Valley, Nepal Himalaya, from 1974 to 2010 Reviewed Open Access

Takayuki Nuimura, Koji Fujita, Akiko Sakai

QUATERNARY INTERNATIONAL Vol. 455 page： 93 - 101 2017.10

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

Topographic controls on the debris-cover extent of glaciers in the Eastern Himalayas: Regional analysis using a novel high-resolution glacier inventory Reviewed

Sunal Ojha, Koji Fujita, Akiko Sakai, Hiroto Nagai, Damodar Lamsal

QUATERNARY INTERNATIONAL Vol. 455 page： 82 - 92 2017.10

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

Evaluating the Scale and Potential of GLOF in the Bhutan Himalayas Using a Satellite-Based Integral Glacier-Glacial Lake Inventory Reviewed

Hiroto Nagai, Jinro Ukita, Chiyuki Narama, Koji Fujita, Akiko Sakai, Takeo Tadono, Tsutomu Yamanokuchi, Nobuhiro Tomiyama

GEOSCIENCES Vol. 7 ( 3 ) page： 77 2017.9

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

Debris-covered glacier anomaly? Morphological factors controlling changes in the mass balance, surface area, terminus position, and snow line altitude of Himalayan glaciers Reviewed

Franco Salerno, Sudeep Thakuri, Gianni Tartari, Takayuki Nnimura, Sojiro Sunako, Akiko Sakai, Koji Fujita

EARTH AND PLANETARY SCIENCE LETTERS Vol. 471 page： 19 - 31 2017.8

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

Anomalous winter-snow-amplified earthquake-induced disaster of the 2015 Langtang avalanche in Nepal Reviewed Open Access

Koji Fujita, Hiroshi Inoue, Takeki Izumi, Satoru Yamaguchi, Ayako Sadakane, Sojiro Sunako, Kouichi Nishimura, WalterW. Immerzeel, Joseph M. Shea, Rijan B. Kayastha, Takanobu Sawagaki, David F. Breashears, Hiroshi Yagi, Akiko Sakai

NATURAL HAZARDS AND EARTH SYSTEM SCIENCES Vol. 17 ( 5 ) page： 749 - 764 2017.5

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

State dependence of climatic instability over the past 720,000 years from Antarctic ice cores and climate modeling Reviewed Open Access

Kenji Kawamura, Ayako Abe-Ouchi, Hideaki Motoyama, Yutaka Ageta, Shuji Aoki, Nobuhiko Azuma, Yoshiyuki Fujii, Koji Fujita, Shuji Fujita, Kotaro Fukui, Teruo Furukawa, Atsushi Furusaki, Kumiko Goto-Azuma, Ralf Greve, Motohiro Hirabayashi, Takeo Hondoh, Akira Hori, Shinichiro Horikawa, Kazuho Horiuchi, Makoto Igarashi, Yoshinori Iizuka, Takao Kameda, Hiroshi Kanda, Mika Kohno, Takayuki Kuramoto, Yuki Matsushi, Morihiro Miyahara, Takayuki Miyake, Atsushi Miyamoto, Yasuo Nagashima, Yoshiki Nakayama, Takakiyo Nakazawa, Fumio Nakazawa, Fumihiko Nishio, Ichio Obinata, Rumi Ohgaito, Akira Oka, Jun'ichi Okuno, Junichi Okuyama, Ikumi Oyabu, Frederic Parrenin, Frank Pattyn, Fuyuki Saito, Takashi Saito, Takeshi Saito, Toshimitsu Sakurai, Kimikazu Sasa, Hakime Seddik, Yasuyuki Shibata, Kunio Shinbori, Keisuke Suzuki, Toshitaka Suzuki, Akiyoshi Takahashi, Kunio Takahashi, Shuhei Takahashi, Morimasa Takata, Yoichi Tanaka, Ryu Uemura, Genta Watanabe, Okitsugu Watanabe, Tetsuhide Yamasaki, Kotaro Yokoyama, Masakazu Yoshimori, Takayasu Yoshimoto

SCIENCE ADVANCES Vol. 3 ( 2 ) page： e1600446 2017.2

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

A firn densification process in the high accumulation dome of southeastern Greenland Reviewed Open Access

Yoshinori Iizuka, Atsushi Miyamoto, Akira Hori, Sumito Matoba, Ryoto Furukawa, Takeshi Saito, Shuji Fujita, Motohiro Hirabayashi, Satoru Yamaguchi, Koji Fujita, Nozomu Takeuchi

ARCTIC ANTARCTIC AND ALPINE RESEARCH Vol. 49 ( 1 ) page： 13 - 27 2017.2

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 > 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 > 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