@article{19878, abstract = {Rock debris partially covers glaciers worldwide, with varying extents and distributions, and controls sub‐debris melt rates by modifying energy transfer from the atmosphere to the ice. Two key physical properties controlling this energy exchange are thermal conductivity (k) and aerodynamic roughness length (z0). Accurate representation of these properties in energy‐balance models is critical for understanding climate‐glacier interactions and predicting the behavior of debris‐covered glaciers. However, k and z0 have been derived at very few sites from limited local measurements, using different approaches, and most model applications rely on values reported from these few sites and studies. We derive k and z0 using established and modified approaches from data at three locations on Pirámide Glacier in the central Chilean Andes. By comparing methods and evaluating melt simulated with an energy‐balance model, we reveal substantial differences between approaches. These lead to discrepancies between ice melt from energy‐balance simulations and observed data, and highlight the impact of method choice on calculated ice melt. Optimizing k against measured melt appears a viable approach to constrain melt simulations. Determining z0 seems less critical, as it has a smaller impact on total melt. Profile aerodynamic method measurements for estimating z0, despite higher costs, are independent of ice melt calculations. The large, unexpected differences between methods indicate a substantial knowledge gap. The fact that field‐derived k and z0 fail to work well in energy‐balance models, suggests that model values represent bulk properties distinct from theoretical field measurements. Addressing this gap is essential for improving glacier melt predictions.}, author = {Melo Velasco, Juan Vicente and Miles, Evan and McCarthy, Michael and Shaw, Thomas and Fyffe, Catriona Louise and Fontrodona-Bach, Adrià and Pellicciotti, Francesca}, issn = {2169-9011}, journal = {Journal of Geophysical Research: Earth Surface}, number = {6}, publisher = {Wiley}, title = {{Method dependence in thermal conductivity and aerodynamic roughness length estimates on a debris‐covered glacier}}, doi = {10.1029/2025jf008360}, volume = {130}, year = {2025}, } @article{12586, abstract = {Ice cliffs are common on debris-covered glaciers and have relatively high melt rates due to their direct exposure to incoming radiation. Previous studies have shown that their number and relative area can change considerably from year to year, but this variability has not been explored, in part because available cliff observations are irregular. Here, we systematically mapped and tracked ice cliffs across four debris-covered glaciers in High Mountain Asia for every late ablation season from 2009 to 2019 using high-resolution multi-spectral satellite imagery. We then quantified the processes occurring at the feature scale to train a stochastic birth-death model to represent the cliff population dynamics. Our results show that while the cliff relative area can change by up to 20% from year to year, the natural long-term variability is constrained, thus defining a glacier-specific cliff carrying capacity. In a subsequent step, the inclusion of external drivers related to climate, glacier dynamics, and hydrology highlights the influence of these variables on the cliff population dynamics, which is usually not a direct one due to the complexity and interdependence of the processes taking place at the glacier surface. In some extreme cases (here, a glacier surge), these external drivers may lead to a reorganization of the cliffs at the glacier surface and a change in the natural variability. These results have implications for the melt of debris-covered glaciers, in addition to showing the high rate of changes at their surface and highlighting some of the links between cliff population and glacier state.}, author = {Kneib, M. and Miles, E. S. and Buri, P. and Molnar, P. and McCarthy, M. and Fugger, S. and Pellicciotti, Francesca}, issn = {2169-9003}, journal = {Journal of Geophysical Research: Earth Surface}, keywords = {Earth-Surface Processes, Geophysics}, number = {10}, publisher = {American Geophysical Union}, title = {{Interannual dynamics of ice cliff populations on debris‐covered glaciers from remote sensing observations and stochastic modeling}}, doi = {10.1029/2021jf006179}, volume = {126}, year = {2021}, } @article{22498, abstract = {Climate change impacts on sediment production and transfer processes on hillslopes and through channels are governed by possible changes in precipitation, runoff, and air temperature. These hydrological and geomorphological impacts are difficult to predict in temperature‐sensitive Alpine environments. In this study, we combined a stochastic weather generator model with the most current climate change projections to feed a hillslope‐channel sediment cascade model for a major debris‐flow system in the Swiss Alps (the Illgraben). This allowed us to quantify climate change impacts and their uncertainties on sediment yield and the number of debris flows at hourly temporal resolution. We show that projected changes in precipitation and air temperature lead to a reduction in both sediment yield (−48%) and debris‐flow occurrence (−23%). This change is caused by a decrease in sediment supply from hillslopes, which is driven by frost‐weathering. Additionally, we conduct model experiments that show the sensitivity of projected changes in sediment yield and debris‐flow hazard to basin elevation, with important implications for assessing natural hazards and risks in mountain environments. Future changes in hydrological and sediment fluxes are characterized by high uncertainty, mainly due to irreducible internal climate variability. Therefore, this stochastic uncertainty needs to be considered in climate change impact assessments for geomorphic systems.}, author = {Hirschberg, Jacob and Fatichi, Simone and Bennett, Georgina L. and McArdell, Brian W. and Peleg, Nadav and Lane, Stuart N. and Schlunegger, Fritz and Molnar, Peter}, issn = {2169-9011}, journal = {Journal of Geophysical Research: Earth Surface}, number = {1}, publisher = {American Geophysical Union}, title = {{Climate change impacts on sediment yield and debris‐flow activity in an alpine catchment}}, doi = {10.1029/2020jf005739}, volume = {126}, year = {2021}, } @article{12613, abstract = {We use high-resolution digital elevation models (DEMs) from unmanned aerial vehicle (UAV) surveys to document the evolution of four ice cliffs on the debris-covered tongue of Lirung Glacier, Nepal, over one ablation season. Observations show that out of four cliffs, three different patterns of evolution emerge: (i) reclining cliffs that flatten during the ablation season; (ii) stable cliffs that maintain a self-similar geometry; and (iii) growing cliffs, expanding laterally. We use the insights from this unique data set to develop a 3-D model of cliff backwasting and evolution that is validated against observations and an independent data set of volume losses. The model includes ablation at the cliff surface driven by energy exchange with the atmosphere, reburial of cliff cells by surrounding debris, and the effect of adjacent ponds. The cliff geometry is updated monthly to account for the modifications induced by each of those processes. Model results indicate that a major factor affecting the survival of steep cliffs is the coupling with ponded water at its base, which prevents progressive flattening and possible disappearance of a cliff. The radial growth observed at one cliff is explained by higher receipts of longwave and shortwave radiation, calculated taking into account atmospheric fluxes, shading, and the emission of longwave radiation from debris surfaces. The model is a clear step forward compared to existing static approaches that calculate atmospheric melt over an invariant cliff geometry and can be used for long-term simulations of cliff evolution and to test existing hypotheses about cliffs' survival.}, author = {Buri, Pascal and Miles, Evan S. and Steiner, Jakob F. and Immerzeel, Walter W. and Wagnon, Patrick and Pellicciotti, Francesca}, issn = {2169-9011}, journal = {Journal of Geophysical Research: Earth Surface}, keywords = {Earth-Surface Processes, Geophysics}, number = {12}, pages = {2471--2493}, publisher = {American Geophysical Union}, title = {{A physically based 3‐D model of ice cliff evolution over debris‐covered glaciers}}, doi = {10.1002/2016jf004039}, volume = {121}, year = {2016}, } @article{22509, abstract = {Hydrologic and geomorphic responses of watersheds to changes in climate are difficult to assess due to projection uncertainties and nonlinearity of the processes that are involved. Yet such assessments are increasingly needed and call for mechanistic approaches within a probabilistic framework. This study employs an integrated hydrology‐geomorphology model, the Triangulated Irregular Network‐based Real‐time Integrated Basin Simulator (tRIBS)‐Erosion, to analyze runoff and erosion sensitivity of seven semiarid headwater basins to projected climate conditions. The Advanced Weather Generator is used to produce two climate ensembles representative of the historic and future climate conditions for the Walnut Gulch Experimental Watershed located in the southwest U.S. The former ensemble incorporates the stochastic variability of the observed climate, while the latter includes the stochastic variability and the uncertainty of multimodel climate change projections. The ensembles are used as forcing for tRIBS‐Erosion that simulates runoff and sediment basin responses leading to probabilistic inferences of future changes. The results show that annual precipitation for the area is generally expected to decrease in the future, with lower hourly intensities and similar daily rates. The smaller hourly rainfall generally results in lower mean annual runoff. However, a non‐negligible probability of runoff increase in the future is identified, resulting from stochastic combinations of years with low and high runoff. On average, the magnitudes of mean and extreme events of sediment yield are expected to decrease with a very high probability. Importantly, the projected variability of annual sediment transport for the future conditions is comparable to that for the historic conditions, despite the fact that the former account for a much wider range of possible climate “alternatives.” This result demonstrates that the historic natural climate variability of sediment yield is already so high, that it is comparable to the variability for a projected and highly uncertain future. Additionally, changes in the scaling relationship between specific sediment yield/runoff and drainage basin area are detected.}, author = {Francipane, A. and Fatichi, Simone and Ivanov, V. Y. and Noto, L. V.}, issn = {2169-9011}, journal = {Journal of Geophysical Research: Earth Surface}, number = {3}, pages = {507--533}, publisher = {American Geophysical Union}, title = {{Stochastic assessment of climate impacts on hydrology and geomorphology of semiarid headwater basins using a physically based model}}, doi = {10.1002/2014jf003232}, volume = {120}, year = {2015}, }