@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}, }