Faculty Profiles - FUJITA, Koji

Papers - FUJITA, Koji

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Glacier preservation doubled by limiting warming to 1.5°C versus 2.7°C Reviewed International coauthorship

Harry Zekollari, Lilian Schuster, Fabien Maussion, Regine Hock, Ben Marzeion, David R. Rounce, Loris Compagno, Koji Fujita, Matthias Huss, Megan James, Philip D. A. Kraaijenbrink, William H. Lipscomb, Samar Minallah, Moritz Oberrauch, Lander Van Tricht, Nicolas Champollion, Tamsin Edwards, Daniel Farinotti, Walter Immerzeel, Gunter Leguy, Akiko Sakai

Science Vol. 388 ( 6750 ) page： 979 - 983 2025.5

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

Glaciers adapt slowly to changing climatic conditions, with long-term implications for sea-level rise and water supply. Using eight glacier models, we simulated global glacier evolution over multicentennial timescales, allowing glaciers to equilibrate with climate under various constant global temperature scenarios. We estimate that glaciers globally will lose 39 (range, 15 to 55)% of their mass relative to 2020, corresponding to a global mean sea-level rise of 113 (range, 43 to 204) mm even if temperatures stabilized at present-day conditions. Under the +1.5°C Paris Agreement goal, more than twice as much global glacier mass remains at equilibration (53% versus 24%) compared with the warming level resulting from current policies (+2.7°C by 2100 above preindustrial). Our findings stress the need for stringent mitigation policies to ensure the long-term preservation of glaciers.

DOI： 10.1126/science.adu4675

Glacier meltwater contribution to river runoff in Western Mongolia Reviewed International coauthorship

Purevdagva Khalzan, Sanjar Sadyrov, Akiko Sakai, Kenji Tanaka, Koji Fujita

Journal of Hydrology: Regional Studies Vol. 59 page： 102375 - 102375 2025.6

Acidity-driven gas-particle partitioning of nitrate regulates its transport to Arctic through the industrial era Reviewed International coauthorship Open Access

Yoshinori Iizuka, Mai Matsumoto, Kaoru Kawakami, Mahiro Sasage, Sakiko Ishino, Shohei Hattori, Ryu Uemura, Hitoshi Matsui, Koji Fujita, Naga Oshima, Andrea Spolaor, Anders Svensson, Bo Møllesøe Vinther, Hiroshi Ohno, Osamu Seki, Sumito Matoba

Nature Communications Vol. 16 ( 1 ) 2025.5

Modelling seasonal fluctuations and aspect characteristics of ice-cliff melt on the debris-covered Trakarding Glacier, Rolwaling Valley, Nepal Himalaya Reviewed International coauthorship Open Access

Yota Sato, Pascal Buri, Marin Kneib, Evan S. Miles, Sojiro Sunako, Tika R. Gurung, Akiko Sakai, Francesca Pellicciotti, Koji Fujita

Journal of Glaciology Vol. 71 page： 1 - 36 2025.4

Contrasting Responses of Ion Concentration Variations to Atmospheric Patterns in Central Himalayan Ice Cores Reviewed International coauthorship

Akane Tsushima, Nao Esashi, Sumito Matoba, Yoshinori Iizuka, Ryu Uemura, Kouji Adachi, Takeshi Kinase, Motohiro Hirabayashi, Kaoru Kawakami, Rijan B. Kayastha, Koji Fujita

Journal of Geophysical Research: Atmospheres Vol. 130 ( 2 ) page： e2024JD042392 2025.1

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

Abstract

We analyzed the water‐soluble chemical composition of an 81.2‐m‐long ice core collected in 2019 from 6,000 m elevation on a south‐facing glacier in the Nepal Himalaya. The ice core chronology is based on variability in nitrate and calcium ions, which reveal an apparently seasonal periodicity (with winter maxima) throughout the core's length. Two annual boundaries are consistent with the tritium peak representing nuclear tests conducted in 1963 CE and with the spike in sulfate ions due to the eruption of Krakatau in 1883 CE. The ice core spans 145 years from 1875 to 2019 CE. Dating uncertainties due to the layer counting methodology were estimated as year for 1963–2019 CE and years for 1875–1963 CE. Comparison with earlier ice cores drilled on the northern side of the Himalayas revealed that the ion components exhibit inverse correlations with two key climatic indices: the North Atlantic Oscillation and Southern Oscillation Index. Composite analysis of reanalysis climate data suggests that these inverse relationships reflect springtime pressure patterns, which show regional differences between the northern and southern sides of the Himalayan range.

DOI： 10.1029/2024JD042392

Web of Science

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

Web of Science

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

Web of Science

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

Web of Science

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

Web of Science

PubMed

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

Web of Science

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

Web of Science

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

Web of Science

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

Web of Science

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

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

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

Web of Science

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

Web of Science

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

Web of Science

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

Web of Science

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

Web of Science

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

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