@article{14885, abstract = {The near-surface boundary layer can mediate the response of mountain glaciers to external climate, cooling the overlying air and promoting a density-driven glacier wind. The fundamental processes are conceptually well understood, though the magnitudes of cooling and presence of glacier winds are poorly quantified in space and time, increasing the forcing uncertainty for melt models. We utilize a new data set of on-glacier meteorological measurements on three neighboring glaciers in the Swiss Alps to explore their distinct response to regional climate under the extreme 2022 summer. We find that synoptic wind origins and local terrain modifications, not only glacier size, play an important role in the ability of a glacier to cool the near-surface air. Warm air intrusions from valley or synoptically-driven winds onto the glacier can occur between ∼19% and 64% of the time and contribute between 3% and 81% of the total sensible heat flux to the surface during warm afternoon hours, depending on the fetch of the glacier flowline and its susceptibility to boundary layer erosion. In the context of extreme summer warmth, indicative of future conditions, the boundary layer cooling (up to 6.5°C cooler than its surroundings) and resultant katabatic wind flow are highly heterogeneous between the study glaciers, highlighting the complex and likely non-linear response of glaciers to an uncertain future.}, author = {Shaw, Thomas and Buri, Pascal and Mccarthy, Michael and Miles, Evan S. and Pellicciotti, Francesca}, issn = {2169-8996}, journal = {Journal of Geophysical Research: Atmospheres}, number = {2}, publisher = {Wiley}, title = {{Local controls on near-surface glacier cooling under warm atmospheric conditions}}, doi = {10.1029/2023JD040214}, volume = {129}, year = {2024}, } @article{14938, abstract = {High elevation headwater catchments are complex hydrological systems that seasonally buffer water and release it in the form of snow and ice melt, modulating downstream runoff regimes and water availability. In High Mountain Asia (HMA), where a wide range of climates from semi-arid to monsoonal exist, the importance of the cryospheric contributions to the water budget varies with the amount and seasonal distribution of precipitation. Losses due to evapotranspiration and sublimation are to date largely unquantified components of the water budget in such catchments, although they can be comparable in magnitude to glacier melt contributions to streamflow. 
Here, we simulate the hydrology of three high elevation headwater catchments in distinct climates in HMA over 10 years using an ecohydrological model geared towards high-mountain areas including snow and glaciers, forced with reanalysis data. 
Our results show that evapotranspiration and sublimation together are most important at the semi-arid site, Kyzylsu, on the northernmost slopes of the Pamir mountain range. Here, the evaporative loss amounts to 28% of the water throughput, which we define as the total water added to, or removed from the water balance within a year. In comparison, evaporative losses are 19% at the Central Himalayan site Langtang and 13% at the wettest site, 24K, on the Southeastern Tibetan Plateau. At the three sites, respectively, sublimation removes 15%, 13% and 6% of snowfall, while evapotranspiration removes the equivalent of 76%, 28% and 19% of rainfall. In absolute terms, and across a comparable elevation range, the highest ET flux is 413 mm yr-1 at 24K, while the highest sublimation flux is 91 mm yr-1 at Kyzylsu. During warm and dry years, glacier melt was found to only partially compensate for the annual supply deficit.}, author = {Fugger, Stefan and Shaw, Thomas and Jouberton, Achille and Miles, Evan and Buri, Pascal and McCarthy, Michael and Fyffe, Catriona Louise and Fatichi, Simone and Kneib, Marin and Molnar, Peter and Pellicciotti, Francesca}, issn = {1748-9326}, journal = {Environmental Research Letters}, keywords = {Public Health, Environmental and Occupational Health, General Environmental Science, Renewable Energy, Sustainability and the Environment}, publisher = {IOP Publishing}, title = {{Hydrological regimes and evaporative flux partitioning at the climatic ends of High Mountain Asia}}, doi = {10.1088/1748-9326/ad25a0}, year = {2024}, } @article{14487, 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.}, author = {Buri, Pascal and Fatichi, Simone and Shaw, Thomas and Miles, Evan S. and Mccarthy, Michael and Fyffe, Catriona Louise and Fugger, Stefan and Ren, Shaoting and Kneib, Marin and Jouberton, Achille and Steiner, Jakob and Fujita, Koji and Pellicciotti, Francesca}, issn = {1944-7973}, journal = {Water Resources Research}, number = {10}, publisher = {Wiley}, title = {{Land surface modeling in the Himalayas: On the importance of evaporative fluxes for the water balance of a high-elevation catchment}}, doi = {10.1029/2022WR033841}, volume = {59}, year = {2023}, } @misc{14494, abstract = {We provide i) gridded initial conditions (.tif), ii) modeled gridded monthly outputs (.tif), and iii) modeled hourly outputs at the station locations (.txt) for the hydrological year 2019. Information about the variables and units can be found in the figures (.png) associated to each dataset. Details about the datasets can be found in the original publication by Buri and others (2023). Buri, P., Fatichi, S., Shaw, T. E., Miles, E. S., McCarthy, M. J., Fyffe, C. L., ... & Pellicciotti, F. (2023). Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment. Water Resources Research, 59(10), e2022WR033841. DOI: 10.1029/2022WR033841}, author = {Buri, Pascal and Fatichi, Simone and Shaw, Thomas and Miles, Evan and McCarthy, Michael and Fyffe, Catriona Louise and Fugger, Stefan and Ren, Shaoting and Kneib, Marin and Jouberton, Achille and Steiner, Jakob and Fujita, Koji and Pellicciotti, Francesca}, publisher = {Zenodo}, title = {{Model output data to "Land surface modeling in the Himalayas: on the importance of evaporative fluxes for the water balance of a high elevation catchment"}}, doi = {10.5281/ZENODO.8402426}, year = {2023}, } @article{14659, abstract = {Understanding the response of Himalayan glaciers to global warming is vital because of their role as a water source for the Asian subcontinent. However, great uncertainties still exist on the climate drivers of past and present glacier changes across scales. Here, we analyse continuous hourly climate station data from a glacierized elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis. We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming. Reanalysis data suggest a broader occurrence of this effect in the glacierized areas of the Himalaya. We hypothesize that the counterintuitive cooling is caused by enhanced sensible heat exchange and the associated increase in glacier katabatic wind, which draws cool air downward from higher elevations. The stronger katabatic winds have also lowered the elevation of local wind convergence, thereby diminishing precipitation in glacial areas and negatively affecting glacier mass balance. This local cooling may have partially preserved glaciers from melting and could help protect the periglacial environment.}, author = {Salerno, Franco and Guyennon, Nicolas and Yang, Kun and Shaw, Thomas and Lin, Changgui and Colombo, Nicola and Romano, Emanuele and Gruber, Stephan and Bolch, Tobias and Alessandri, Andrea and Cristofanelli, Paolo and Putero, Davide and Diolaiuti, Guglielmina and Tartari, Gianni and Verza, Gianpietro and Thakuri, Sudeep and Balsamo, Gianpaolo and Miles, Evan S. and Pellicciotti, Francesca}, issn = {1752-0908}, journal = {Nature Geoscience}, pages = {1120--1127}, publisher = {Springer Nature}, title = {{Local cooling and drying induced by Himalayan glaciers under global warming}}, doi = {10.1038/s41561-023-01331-y}, volume = {16}, year = {2023}, } @article{14779, abstract = {The presence of a developed boundary layer decouples a glacier's response from ambient conditions, suggesting that sensitivity to climate change is increased by glacier retreat. To test this hypothesis, we explore six years of distributed meteorological data on a small Swiss glacier in the period 2001–2022. Large glacier fragmentation has occurred since 2001 (−35% area change up to 2022) coinciding with notable frontal retreat, an observed switch from down‐glacier katabatic to up‐glacier valley winds and an increased sensitivity (ratio) of on‐glacier to off‐glacier temperature. As the glacier ceases to develop density‐driven katabatic winds, sensible heat fluxes on the glacier are increasingly determined by the conditions occurring outside the boundary layer of the glacier, sealing the glacier's demise as the climate continues to warm and experience an increased frequency of extreme summers.}, author = {Shaw, Thomas E. and Buri, Pascal and McCarthy, Michael and Miles, Evan S. and Ayala, Álvaro and Pellicciotti, Francesca}, issn = {1944-8007}, journal = {Geophysical Research Letters}, keywords = {General Earth and Planetary Sciences, Geophysics}, number = {11}, publisher = {American Geophysical Union}, title = {{The decaying near‐surface boundary layer of a retreating alpine glacier}}, doi = {10.1029/2023gl103043}, volume = {50}, year = {2023}, } @misc{14919, abstract = {GLACIER METEOROLOGICAL DATA SWISS ALPS -2022 }, author = {Shaw, Thomas and Buri, Pascal and McCarthy, Michael and Miles, Evan and Pellicciotti, Francesca}, publisher = {Zenodo}, title = {{Air temperature and near-surface meteorology datasets on three Swiss glaciers - Extreme 2022 Summer}}, doi = {10.5281/ZENODO.8277285}, year = {2023}, } @article{12573, abstract = {Supraglacial debris strongly modulates glacier melt rates and can be decisive for ice dynamics and mountain hydrology. It is ubiquitous in High-Mountain Asia, yet because its thickness and supply rate from local topography are poorly known, our ability to forecast regional glacier change and streamflow is limited. Here we combined remote sensing and numerical modelling to resolve supraglacial debris thickness by altitude for 4689 glaciers in High-Mountain Asia, and debris-supply rate to 4141 of those glaciers. Our results reveal extensively thin supraglacial debris and high spatial variability in both debris thickness and supply rate. Debris-supply rate increases with the temperature and slope of debris-supply slopes regionally, and debris thickness increases as ice flow decreases locally. Our centennial-scale estimates of debris-supply rate are typically an order of magnitude or more lower than millennial-scale estimates of headwall-erosion rate from Beryllium-10 cosmogenic nuclides, potentially reflecting episodic debris supply to the region’s glaciers.}, author = {McCarthy, Michael and Miles, Evan and Kneib, Marin and Buri, Pascal and Fugger, Stefan and Pellicciotti, Francesca}, issn = {2662-4435}, journal = {Communications Earth & Environment}, keywords = {General Earth and Planetary Sciences, General Environmental Science}, publisher = {Springer Nature}, title = {{Supraglacial debris thickness and supply rate in High-Mountain Asia}}, doi = {10.1038/s43247-022-00588-2}, volume = {3}, year = {2022}, } @article{12574, abstract = {Melt from supraglacial ice cliffs is an important contributor to the mass loss of debris-covered glaciers. However, ice cliff contribution is difficult to quantify as they are highly dynamic features, and the paucity of observations of melt rates and their variability leads to large modelling uncertainties. We quantify monsoon season melt and 3D evolution of four ice cliffs over two debris-covered glaciers in High Mountain Asia (Langtang Glacier, Nepal, and 24K Glacier, China) at very high resolution using terrestrial photogrammetry applied to imagery captured from time-lapse cameras installed on lateral moraines. We derive weekly flow-corrected digital elevation models (DEMs) of the glacier surface with a maximum vertical bias of ±0.2 m for Langtang Glacier and ±0.05 m for 24K Glacier and use change detection to determine distributed melt rates at the surfaces of the ice cliffs throughout the study period. We compare the measured melt patterns with those derived from a 3D energy balance model to derive the contribution of the main energy fluxes. We find that ice cliff melt varies considerably throughout the melt season, with maximum melt rates of 5 to 8 cm d−1, and their average melt rates are 11–14 (Langtang) and 4.5 (24K) times higher than the surrounding debris-covered ice. Our results highlight the influence of redistributed supraglacial debris on cliff melt. At both sites, ice cliff albedo is influenced by the presence of thin debris at the ice cliff surface, which is largely controlled on 24K Glacier by liquid precipitation events that wash away this debris. Slightly thicker or patchy debris reduces melt by 1–3 cm d−1 at all sites. Ultimately, our observations show a strong spatio-temporal variability in cliff area at each site, which is controlled by supraglacial streams and ponds and englacial cavities that promote debris slope destabilisation and the lateral expansion of the cliffs. These findings highlight the need to better represent processes of debris redistribution in ice cliff models, to in turn improve estimates of ice cliff contribution to glacier melt and the long-term geomorphological evolution of debris-covered glacier surfaces.}, author = {Kneib, Marin and Miles, Evan S. and Buri, Pascal and Fugger, Stefan and McCarthy, Michael and Shaw, Thomas E. and Chuanxi, Zhao and Truffer, Martin and Westoby, Matthew J. and Yang, Wei and Pellicciotti, Francesca}, issn = {1994-0424}, journal = {The Cryosphere}, keywords = {Earth-Surface Processes, Water Science and Technology}, number = {11}, pages = {4701--4725}, publisher = {Copernicus Publications}, title = {{Sub-seasonal variability of supraglacial ice cliff melt rates and associated processes from time-lapse photogrammetry}}, doi = {10.5194/tc-16-4701-2022}, volume = {16}, year = {2022}, } @article{12575, abstract = {The current Chilean megadrought has led to acute water shortages in central Chile since 2010. Glaciers have provided vital fresh water to the region's rivers, but the quantity, timing and sustainability of that provision remain unclear. Here we combine in-situ, remote sensing and climate reanalysis data to show that from 2010 to 2018 during the megadrought, unsustainable imbalance ablation of glaciers (ablation not balanced by new snowfall) strongly buffered the late-summer discharge of the Maipo River, a primary source of water to Santiago. If there had been no glaciers, water availability would have been reduced from December through May, with a 31 ± 19% decrease during March. Our results indicate that while the annual contributions of imbalance ablation to river discharge during the megadrought have been small compared to those from precipitation and sustainable balance ablation, they have nevertheless been a substantial input to a hydrological system that was already experiencing high water stress. The water-equivalent volume of imbalance ablation generated in the Maipo Basin between 2010 and 2018 was 740 × 106 m3 (19 ± 12 mm yr−1), approximately 3.4 times the capacity of the basin's El Yeso Reservoir. This is equivalent to 14% of Santiago's potable water use in that time, while total glacier ablation was equivalent to 59%. We show that glacier retreat will exacerbate river discharge deficits and further jeopardize water availability in central Chile if precipitation deficits endure, and conjecture that these effects will be amplified by climatic warming.}, author = {McCarthy, Michael and Meier, Fabienne and Fatichi, Simone and Stocker, Benjamin D. and Shaw, Thomas E. and Miles, Evan and Dussaillant, Inés and Pellicciotti, Francesca}, issn = {2328-4277}, journal = {Earth's Future}, keywords = {Earth and Planetary Sciences (miscellaneous), General Environmental Science}, number = {10}, publisher = {American Geophysical Union}, title = {{Glacier contributions to river discharge during the current Chilean megadrought}}, doi = {10.1029/2022ef002852}, volume = {10}, year = {2022}, } @article{12576, 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.}, author = {Shaw, T E and Miles, E S and Chen, D and Jouberton, A and Kneib, M and Fugger, S and Ou, T and Lai, H-W and Fujita, K and Yang, W and Fatichi, S and Pellicciotti, Francesca}, issn = {1748-9326}, journal = {Environmental Research Letters}, keywords = {Public Health, Environmental and Occupational Health, General Environmental Science, Renewable Energy, Sustainability and the Environment}, number = {10}, publisher = {IOP Publishing}, title = {{Multi-decadal monsoon characteristics and glacier response in High Mountain Asia}}, doi = {10.1088/1748-9326/ac9008}, volume = {17}, year = {2022}, } @article{12577, abstract = {Glaciers are key components of the mountain water towers of Asia and are vital for downstream domestic, agricultural, and industrial uses. The glacier mass loss rate over the southeastern Tibetan Plateau is among the highest in Asia and has accelerated in recent decades. This acceleration has been attributed to increased warming, but the mechanisms behind these glaciers’ high sensitivity to warming remain unclear, while the influence of changes in precipitation over the past decades is poorly quantified. Here, we reconstruct glacier mass changes and catchment runoff since 1975 at a benchmark glacier, Parlung No. 4, to shed light on the drivers of recent mass losses for the monsoonal, spring-accumulation glaciers of the Tibetan Plateau. Our modeling demonstrates how a temperature increase (mean of 0.39∘C ⋅dec−1since 1990) has accelerated mass loss rates by altering both the ablation and accumulation regimes in a complex manner. The majority of the post-2000 mass loss occurred during the monsoon months, caused by simultaneous decreases in the solid precipitation ratio (from 0.70 to 0.56) and precipitation amount (–10%), leading to reduced monsoon accumulation (–26%). Higher solid precipitation in spring (+18%) during the last two decades was increasingly important in mitigating glacier mass loss by providing mass to the glacier and protecting it from melting in the early monsoon. With bare ice exposed to warmer temperatures for longer periods, icemelt and catchment discharge have unsustainably intensified since the start of the 21st century, raising concerns for long-term water supply and hazard occurrence in the region.}, author = {Jouberton, Achille and Shaw, Thomas E. and Miles, Evan and McCarthy, Michael and Fugger, Stefan and Ren, Shaoting and Dehecq, Amaury and Yang, Wei and Pellicciotti, Francesca}, issn = {1091-6490}, journal = {PNAS}, keywords = {Multidisciplinary}, number = {37}, publisher = {Proceedings of the National Academy of Sciences}, title = {{Warming-induced monsoon precipitation phase change intensifies glacier mass loss in the southeastern Tibetan Plateau}}, doi = {10.1073/pnas.2109796119}, volume = {119}, year = {2022}, } @article{12578, abstract = {Currently, about 12 %–13 % of High Mountain Asia’s glacier area is debris-covered, which alters its surface mass balance. However, in regional-scale modelling approaches, debris-covered glaciers are typically treated as clean-ice glaciers, leading to a bias when modelling their future evolution. Here, we present a new approach for modelling debris area and thickness evolution, applicable from single glaciers to the global scale. We derive a parameterization and implement it as a module into the Global Glacier Evolution Model (GloGEMflow), a combined mass-balance ice-flow model. The module is initialized with both glacier-specific observations of the debris' spatial distribution and estimates of debris thickness. These data sets account for the fact that debris can either enhance or reduce surface melt depending on thickness. Our model approach also enables representing the spatiotemporal evolution of debris extent and thickness. We calibrate and evaluate the module on a selected subset of glaciers and apply GloGEMflow using different climate scenarios to project the future evolution of all glaciers in High Mountain Asia until 2100. Explicitly accounting for debris cover has only a minor effect on the projected mass loss, which is in line with previous projections. Despite this small effect, we argue that the improved process representation is of added value when aiming at capturing intra-glacier scales, i.e. spatial mass-balance distribution. Depending on the climate scenario, the mean debris-cover fraction is expected to increase, while mean debris thickness is projected to show only minor changes, although large local thickening is expected. To isolate the influence of explicitly accounting for supraglacial debris cover, we re-compute glacier evolution without the debris-cover module. We show that glacier geometry, area, volume, and flow velocity evolve differently, especially at the level of individual glaciers. This highlights the importance of accounting for debris cover and its spatiotemporal evolution when projecting future glacier changes.}, author = {Compagno, Loris and Huss, Matthias and Miles, Evan Stewart and McCarthy, Michael James and Zekollari, Harry and Dehecq, Amaury and Pellicciotti, Francesca and Farinotti, Daniel}, issn = {1994-0424}, journal = {The Cryosphere}, keywords = {Earth-Surface Processes, Water Science and Technology}, number = {5}, pages = {1697--1718}, publisher = {Copernicus Publications}, title = {{Modelling supraglacial debris-cover evolution from the single-glacier to the regional scale: An application to High Mountain Asia}}, doi = {10.5194/tc-16-1697-2022}, volume = {16}, year = {2022}, } @article{12579, abstract = {The Indian and East Asian summer monsoons shape the melt and accumulation patterns of glaciers in High Mountain Asia in complex ways due to the interaction of persistent cloud cover, large temperature ranges, high atmospheric water content and high precipitation rates. Glacier energy- and mass-balance modelling using in situ measurements offers insights into the ways in which surface processes are shaped by climatic regimes. In this study, we use a full energy- and mass-balance model and seven on-glacier automatic weather station datasets from different parts of the Central and Eastern Himalaya to investigate how monsoon conditions influence the glacier surface energy and mass balance. In particular, we look at how debris-covered and debris-free glaciers respond differently to monsoonal conditions. The radiation budget primarily controls the melt of clean-ice glaciers, but turbulent fluxes play an important role in modulating the melt energy on debris-covered glaciers. The sensible heat flux decreases during core monsoon, but the latent heat flux cools the surface due to evaporation of liquid water. This interplay of radiative and turbulent fluxes causes debris-covered glacier melt rates to stay almost constant through the different phases of the monsoon. Ice melt under thin debris, on the other hand, is amplified by both the dark surface and the turbulent fluxes, which intensify melt during monsoon through surface heating and condensation. Pre-monsoon snow cover can considerably delay melt onset and have a strong impact on the seasonal mass balance. Intermittent monsoon snow cover lowers the melt rates at high elevation. This work is fundamental to the understanding of the present and future Himalayan cryosphere and water budget, while informing and motivating further glacier- and catchment-scale research using process-based models.}, author = {Fugger, Stefan and Fyffe, Catriona L. and Fatichi, Simone and Miles, Evan and McCarthy, Michael and Shaw, Thomas E. and Ding, Baohong and Yang, Wei and Wagnon, Patrick and Immerzeel, Walter and Liu, Qiao and Pellicciotti, Francesca}, issn = {1994-0424}, journal = {The Cryosphere}, keywords = {Earth-Surface Processes, Water Science and Technology}, number = {5}, pages = {1631--1652}, publisher = {Copernicus Publications}, title = {{Understanding monsoon controls on the energy and mass balance of glaciers in the Central and Eastern Himalaya}}, doi = {10.5194/tc-16-1631-2022}, volume = {16}, year = {2022}, } @article{12580, abstract = {River systems originating from the Upper Indus Basin (UIB) are dominated by runoff from snow and glacier melt and summer monsoonal rainfall. These water resources are highly stressed as huge populations of people living in this region depend on them, including for agriculture, domestic use, and energy production. Projections suggest that the UIB region will be affected by considerable (yet poorly quantified) changes to the seasonality and composition of runoff in the future, which are likely to have considerable impacts on these supplies. Given how directly and indirectly communities and ecosystems are dependent on these resources and the growing pressure on them due to ever-increasing demands, the impacts of climate change pose considerable adaptation challenges. The strong linkages between hydroclimate, cryosphere, water resources, and human activities within the UIB suggest that a multi- and inter-disciplinary research approach integrating the social and natural/environmental sciences is critical for successful adaptation to ongoing and future hydrological and climate change. Here we use a horizon scanning technique to identify the Top 100 questions related to the most pressing knowledge gaps and research priorities in social and natural sciences on climate change and water in the UIB. These questions are on the margins of current thinking and investigation and are clustered into 14 themes, covering three overarching topics of “governance, policy, and sustainable solutions”, “socioeconomic processes and livelihoods”, and “integrated Earth System processes”. Raising awareness of these cutting-edge knowledge gaps and opportunities will hopefully encourage researchers, funding bodies, practitioners, and policy makers to address them.}, author = {Orr, Andrew and Ahmad, Bashir and Alam, Undala and Appadurai, ArivudaiNambi and Bharucha, Zareen P. and Biemans, Hester and Bolch, Tobias and Chaulagain, Narayan P. and Dhaubanjar, Sanita and Dimri, A. P. and Dixon, Harry and Fowler, Hayley J. and Gioli, Giovanna and Halvorson, Sarah J. and Hussain, Abid and Jeelani, Ghulam and Kamal, Simi and Khalid, Imran S. and Liu, Shiyin and Lutz, Arthur and Mehra, Meeta K. and Miles, Evan and Momblanch, Andrea and Muccione, Veruska and Mukherji, Aditi and Mustafa, Daanish and Najmuddin, Omaid and Nasimi, Mohammad N. and Nüsser, Marcus and Pandey, Vishnu P. and Parveen, Sitara and Pellicciotti, Francesca and Pollino, Carmel and Potter, Emily and Qazizada, Mohammad R. and Ray, Saon and Romshoo, Shakil and Sarkar, Syamal K. and Sawas, Amiera and Sen, Sumit and Shah, Attaullah and Shah, M. Azeem Ali and Shea, Joseph M. and Sheikh, Ali T. and Shrestha, Arun B. and Tayal, Shresth and Tigala, Snehlata and Virk, Zeeshan T. and Wester, Philippus and Wescoat, James L.}, issn = {2328-4277}, journal = {Earth's Future}, keywords = {Earth and Planetary Sciences (miscellaneous), General Environmental Science}, number = {4}, publisher = {American Geophysical Union}, title = {{Knowledge priorities on climate change and water in the Upper Indus Basin: A horizon scanning exercise to identify the Top 100 research questions in social and natural sciences}}, doi = {10.1029/2021ef002619}, volume = {10}, year = {2022}, } @article{12581, abstract = {Topographic development via paraglacial slope failure (PSF) represents a complex interplay between geological structure, climate, and glacial denudation. Southeastern Tibet has experienced amongst the highest rates of ice mass loss in High Mountain Asia in recent decades, but few studies have focused on the implications of this mass loss on the stability of paraglacial slopes. We used repeat satellite- and unpiloted aerial vehicle (UAV)-derived imagery between 1990 and 2020 as the basis for mapping PSFs from slopes adjacent to Hailuogou Glacier (HLG), a 5 km long monsoon temperate valley glacier in the Mt. Gongga region. We observed recent lowering of the glacier tongue surface at rates of up to 0.88 m a−1 in the period 2000 to 2016, whilst overall paraglacial bare ground area (PBGA) on glacier-adjacent slopes increased from 0.31 ± 0.27 km2 in 1990 to 1.38 ± 0.06 km2 in 2020. Decadal PBGA expansion rates were ∼ 0.01 km2 a−1, 0.02 km2 a−1, and 0.08 km2 in the periods 1990–2000, 2000–2011, and 2011–2020 respectively, indicating an increasing rate of expansion of PBGA. Three types of PSFs, including rockfalls, sediment-mantled slope slides, and headward gully erosion, were mapped, with a total area of 0.75 ± 0.03 km2 in 2020. South-facing valley slopes (true left of the glacier) exhibited more destabilization (56 % of the total PSF area) than north-facing (true right) valley slopes (44 % of the total PSF area). Deformation of sediment-mantled moraine slopes (mean 1.65–2.63 ± 0.04 cm d−1) and an increase in erosion activity in ice-marginal tributary valleys caused by a drop in local base level (gully headward erosion rates are 0.76–3.39 cm d−1) have occurred in tandem with recent glacier downwasting. We also observe deformation of glacier ice, possibly driven by destabilization of lateral moraine, as has been reported in other deglaciating mountain glacier catchments. The formation, evolution, and future trajectory of PSFs at HLG (as well as other monsoon-dominated deglaciating mountain areas) are related to glacial history, including recent rapid downwasting leading to the exposure of steep, unstable bedrock and moraine slopes, and climatic conditions that promote slope instability, such as very high seasonal precipitation and seasonal temperature fluctuations that are conducive to freeze–thaw and ice segregation processes.}, author = {Zhong, Yan and Liu, Qiao and Westoby, Matthew and Nie, Yong and Pellicciotti, Francesca and Zhang, Bo and Cai, Jialun and Liu, Guoxiang and Liao, Haijun and Lu, Xuyang}, issn = {2196-632X}, journal = {Earth Surface Dynamics}, keywords = {Earth-Surface Processes, Geophysics}, number = {1}, pages = {23--42}, publisher = {Copernicus Publications}, title = {{Intensified paraglacial slope failures due to accelerating downwasting of a temperate glacier in Mt. Gongga, southeastern Tibetan Plateau}}, doi = {10.5194/esurf-10-23-2022}, volume = {10}, year = {2022}, } @article{12582, abstract = {Supraglacial debris covers 7% of mountain glacier area globally and generally reduces glacier surface melt. Enhanced energy absorption at ice cliffs and supraglacial ponds scattered across the debris surface leads these features to contribute disproportionately to glacier-wide ablation. However, the degree to which cliffs and ponds actually increase melt rates remains unclear, as these features have only been studied in a detailed manner for selected locations, almost exclusively in High Mountain Asia. In this study we model the surface energy balance for debris-covered ice, ice cliffs, and supraglacial ponds with a set of automatic weather station records representing the global prevalence of debris-covered glacier ice. We generate 5000 random sets of values for physical parameters using probability distributions derived from literature, which we use to investigate relative melt rates and to isolate the melt responses of debris, cliffs and ponds to the site-specific meteorological forcing. Modelled sub-debris melt rates are primarily controlled by debris thickness and thermal conductivity. At a reference thickness of 0.1 m, sub-debris melt rates vary considerably, differing by up to a factor of four between sites, mainly attributable to air temperature differences. We find that melt rates for ice cliffs are consistently 2–3× the melt rate for clean glacier ice, but this melt enhancement decays with increasing clean ice melt rates. Energy absorption at supraglacial ponds is dominated by latent heat exchange and is therefore highly sensitive to wind speed and relative humidity, but is generally less than for clean ice. Our results provide reference melt enhancement factors for melt modelling of debris-covered glacier sites, globally, while highlighting the need for direct measurement of debris-covered glacier surface characteristics, physical parameters, and local meteorological conditions at a variety of sites around the world.}, author = {Miles, E S and Steiner, J F and Buri, P and Immerzeel, W W and Pellicciotti, Francesca}, issn = {1748-9326}, journal = {Environmental Research Letters}, keywords = {Public Health, Environmental and Occupational Health, General Environmental Science, Renewable Energy, Sustainability and the Environment}, number = {6}, publisher = {IOP Publishing}, title = {{Controls on the relative melt rates of debris-covered glacier surfaces}}, doi = {10.1088/1748-9326/ac6966}, volume = {17}, year = {2022}, } @article{12583, abstract = {Peruvian glaciers are important contributors to dry season runoff for agriculture and hydropower, but they are at risk of disappearing due to climate change. We applied a physically based, energy balance melt model at five on-glacier sites within the Peruvian Cordilleras Blanca and Vilcanota. Net shortwave radiation dominates the energy balance, and despite this flux being higher in the dry season, melt rates are lower due to losses from net longwave radiation and the latent heat flux. The sensible heat flux is a relatively small contributor to melt energy. At three of the sites the wet season snowpack was discontinuous, forming and melting within a daily to weekly timescale, and resulting in highly variable melt rates closely related to precipitation dynamics. Cold air temperatures due to a strong La Niña year at Shallap Glacier (Cordillera Blanca) resulted in a continuous wet season snowpack, significantly reducing wet season ablation. Sublimation was most important at the highest site in the accumulation zone of the Quelccaya Ice Cap (Cordillera Vilcanota), accounting for 81% of ablation, compared to 2%–4% for the other sites. Air temperature and precipitation inputs were perturbed to investigate the climate sensitivity of the five glaciers. At the lower sites warmer air temperatures resulted in a switch from snowfall to rain, so that ablation was increased via the decrease in albedo and increase in net shortwave radiation. At the top of Quelccaya Ice Cap warming caused melting to replace sublimation so that ablation increased nonlinearly with air temperature.}, author = {Fyffe, Catriona L. and Potter, Emily and Fugger, Stefan and Orr, Andrew and Fatichi, Simone and Loarte, Edwin and Medina, Katy and Hellström, Robert Å. and Bernat, Maud and Aubry‐Wake, Caroline and Gurgiser, Wolfgang and Perry, L. Baker and Suarez, Wilson and Quincey, Duncan J. and Pellicciotti, Francesca}, issn = {2169-8996}, journal = {Journal of Geophysical Research: Atmospheres}, keywords = {Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Atmospheric Science, Geophysics}, number = {23}, publisher = {American Geophysical Union}, title = {{The energy and mass balance of Peruvian Glaciers}}, doi = {10.1029/2021jd034911}, volume = {126}, year = {2021}, } @article{12584, abstract = {This project explored the integrated use of satellite, ground observations and hydrological distributed models to support water resources assessment and monitoring in High Mountain Asia (HMA). Hydrological data products were generated taking advantage of the synergies of European and Chinese data assets and space-borne observation systems. Energy-budget-based glacier mass balance and hydrological models driven by satellite observations were developed. These models can be applied to describe glacier-melt contribution to river flow. Satellite hydrological data products were used for forcing, calibration, validation and data assimilation in distributed river basin models. A pilot study was carried out on the Red River basin. Multiple hydrological data products were generated using the data collected by Chinese satellites. A new Evapo-Transpiration (ET) dataset from 2000 to 2018 was generated, including plant transpiration, soil evaporation, rainfall interception loss, snow/ice sublimation and open water evaporation. Higher resolution data were used to characterize glaciers and their response to environmental forcing. These studies focused on the Parlung Zangbo Basin, where glacier facies were mapped with GaoFeng (GF), Sentinal-2/Multi-Spectral Imager (S2/MSI) and Landsat8/Operational Land Imager (L8/OLI) data. The geodetic mass balance was estimated between 2000 and 2017 with Zi-Yuan (ZY)-3 Stereo Images and the SRTM DEM. Surface velocity was studied with Landsat5/Thematic Mapper (L5/TM), L8/OLI and S2/MSI data over the period 2013–2019. An updated method was developed to improve the retrieval of glacier albedo by correcting glacier reflectance for anisotropy, and a new dataset on glacier albedo was generated for the period 2001–2020. A detailed glacier energy and mass balance model was developed with the support of field experiments at the Parlung No. 4 Glacier and the 24 K Glacier, both in the Tibetan Plateau. Besides meteorological measurements, the field experiments included glaciological and hydrological measurements. The energy balance model was formulated in terms of enthalpy for easier treatment of water phase transitions. The model was applied to assess the spatial variability in glacier melt. In the Parlung No. 4 Glacier, the accumulated glacier melt was between 1.5 and 2.5 m w.e. in the accumulation zone and between 4.5 and 6.0 m w.e. in the ablation zone, reaching 6.5 m w.e. at the terminus. The seasonality in the glacier mass balance was observed by combining intensive field campaigns with continuous automatic observations. The linkage of the glacier and snowpack mass balance with water resources in a river basin was analyzed in the Chiese (Italy) and Heihe (China) basins by developing and applying integrated hydrological models using satellite retrievals in multiple ways. The model FEST-WEB was calibrated using retrievals of Land Surface Temperature (LST) to map soil hydrological properties. A watershed model was developed by coupling ecohydrological and socioeconomic systems. Integrated modeling is supported by an updated and parallelized data assimilation system. The latter exploits retrievals of brightness temperature (Advanced Microwave Scanning Radiometer, AMSR), LST (Moderate Resolution Imaging Spectroradiometer, MODIS), precipitation (Tropical Rainfall Measuring Mission (TRMM) and FengYun (FY)-2D) and in-situ measurements. In the case study on the Red River Basin, a new algorithm has been applied to disaggregate the SMOS (Soil Moisture and Ocean Salinity) soil moisture retrievals by making use of the correlation between evaporative fraction and soil moisture.}, author = {Menenti, Massimo and Li, Xin and Jia, Li and Yang, Kun and Pellicciotti, Francesca and Mancini, Marco and Shi, Jiancheng and Escorihuela, Maria José and Zheng, Chaolei and Chen, Qiting and Lu, Jing and Zhou, Jie and Hu, Guangcheng and Ren, Shaoting and Zhang, Jing and Liu, Qinhuo and Qiu, Yubao and Huang, Chunlin and Zhou, Ji and Han, Xujun and Pan, Xiaoduo and Li, Hongyi and Wu, Yerong and Ding, Baohong and Yang, Wei and Buri, Pascal and McCarthy, Michael J. and Miles, Evan S. and Shaw, Thomas E. and Ma, Chunfeng and Zhou, Yanzhao and Corbari, Chiara and Li, Rui and Zhao, Tianjie and Stefan, Vivien and Gao, Qi and Zhang, Jingxiao and Xie, Qiuxia and Wang, Ning and Sun, Yibo and Mo, Xinyu and Jia, Junru and Jouberton, Achille Pierre and Kneib, Marin and Fugger, Stefan and Paciolla, Nicola and Paolini, Giovanni}, issn = {2072-4292}, journal = {Remote Sensing}, keywords = {General Earth and Planetary Sciences}, number = {24}, publisher = {MDPI}, title = {{Multi-source hydrological data products to monitor High Asian river basins and regional water security}}, doi = {10.3390/rs13245122}, volume = {13}, year = {2021}, } @article{12585, abstract = {Glaciers in High Mountain Asia generate meltwater that supports the water needs of 250 million people, but current knowledge of annual accumulation and ablation is limited to sparse field measurements biased in location and glacier size. Here, we present altitudinally-resolved specific mass balances (surface, internal, and basal combined) for 5527 glaciers in High Mountain Asia for 2000–2016, derived by correcting observed glacier thinning patterns for mass redistribution due to ice flow. We find that 41% of glaciers accumulated mass over less than 20% of their area, and only 60% ± 10% of regional annual ablation was compensated by accumulation. Even without 21st century warming, 21% ± 1% of ice volume will be lost by 2100 due to current climatic-geometric imbalance, representing a reduction in glacier ablation into rivers of 28% ± 1%. The ablation of glaciers in the Himalayas and Tien Shan was mostly unsustainable and ice volume in these regions will reduce by at least 30% by 2100. The most important and vulnerable glacier-fed river basins (Amu Darya, Indus, Syr Darya, Tarim Interior) were supplied with >50% sustainable glacier ablation but will see long-term reductions in ice mass and glacier meltwater supply regardless of the Karakoram Anomaly.}, author = {Miles, Evan and McCarthy, Michael and Dehecq, Amaury and Kneib, Marin and Fugger, Stefan and Pellicciotti, Francesca}, issn = {2041-1723}, journal = {Nature Communications}, keywords = {General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}, publisher = {Springer Nature}, title = {{Health and sustainability of glaciers in High Mountain Asia}}, doi = {10.1038/s41467-021-23073-4}, volume = {12}, year = {2021}, }