Basal sliding is an important component of ice motion that is integrated into ice flow models via the use of a friction law, which relates basal shear stress to basal sliding speed and effective pressure. Recent two-way model coupling has utilized temporally changing effective pressure from subglacial hydrology models to drive ice dynamics models. However, there is still significant work required to understand how the friction law impacts such two-way coupled models. Here, we use the Siple Coast, West Antarctica, as a case study to examine these impacts. We compare the Budd and Schoof friction laws, as well as two new regularized Coulomb friction laws that we propose, which respond to changes in ice speed and effective pressure in a way that is consistent with subglacial conditions predicted from subglacial hydrology modeling. We find that the Budd and Schoof friction laws struggle to operate with two-way coupled modeling, leading to a non-physically large speedup of ice in the interior of the ice sheet. Instead, the new friction laws that we propose do not lead to such instabilities in ice motion, producing more physically realistic ice flow outputs.

Glaciers are critical freshwater reservoirs in the Central Andes. Although supraglacial debris covers over 40% of the glacierised area in the Atlantic basins, the long-term surface evolution of debris-covered glaciers remains poorly constrained. In this study, we quantify glacier surface evolution over four decades (1985–2024) for 229 debris-covered glaciers across five major Atlantic basins in the Central Andes. Using ANDESMAG, a Python-based decision-tree algorithm employing spectral thresholds, we analysed more than 60 000 Landsat and Sentinel-2 image tiles in Google Earth Engine. Overall, debris-covered area increased by $20\pm11$% and debris-emergence elevation rose by $122\pm99$ m, while snowline altitude at the end of summer increased by $181\pm91$ m and snow-cover ratio declined by $9\pm11$%. Most of these changes occurred after 2009, during the Central Andes Megadrought, and correlated more strongly with declining precipitation than with rising air temperature. Our open-access workflow, which achieves a classification accuracy of 94%, provides the first annual regional assessment of debris-covered glacier surface evolution in the Central Andes of Argentina. Our results highlight the vulnerability of debris-covered glaciers to ongoing climate change and offer a transferable tool applicable to glacierised mountain regions worldwide.

This study presents a methodology for measuring complex electric permittivity of snow in the 200 MHz–2 GHz frequency range using resonant probes connected to a portable vector network analyzer (VNA). The methodology was applied during two field campaigns performed in the Alps in June and July 2024 under dense wet snow conditions. Snow liquid water content (LWC) and density were retrieved from dielectric measurements and compared with reference values obtained by melting calorimetry and gravimetric sampling, respectively. Two in situ protocols were adopted: a vertical profiling approach in June and a co-located acquisition protocol in July, in which dielectric, calorimetric and gravimetric measurements were performed at the same sampling points. Complex permittivity values measured by the VNA were compared with predictions from different models available in the literature, using reference LWC and density values as inputs. The results indicate that the Sihvola and Tiuri model provides one of the most consistent overall agreements with the experimental data and highlights the importance of co-located acquisitions for reducing the impact of spatial heterogeneity. The proposed methodology represents a field-deployable evolution of traditional snow dielectric measurements, providing encouraging results for LWC estimation while indicating the need for further validation of density retrievals.

Changes in ice surface elevation and slope influence subglacial water pressure and sliding velocity. Leveraging changes in elevation observed by the Ice, Cloud and land-Elevation satellite (ICESat) and ICESat-2 missions, we use coupled subglacial hydrology–ice dynamics modeling applied to a section of the northwest Greenland ice sheet to explore (i) how decadal-scale changes in ice surface elevation influence changes in winter background subglacial hydrology and corresponding ice velocity, and (ii) how much seasonal response is attributable to geometry versus environmental forcing. Our simulations suggest complex reorganization of the subglacial hydrologic system between 2004 and 2020, resulting from changes in surface elevation, driving redistribution of freshwater flux, an overall acceleration trend in the interior and an increase in background basal melt. Without changing hydrological conditions, geometry changes alone lead to greater interior acceleration, suggesting that changes in the subglacial system help to mitigate this speedup. We also find that the winter background state of the subglacial system modulates the seasonal response. This work demonstrates feedbacks that influence mass loss from the Greenland ice sheet as surface elevation evolves, highlighting the subtleties involved in accounting for changes in effective pressure, ice velocity and basal melt due to changes in subglacial hydrology.

Eskers are used to characterize glacial drainage systems to inform ice-sheet modeling. However, the connection between eskers preserved in the paleoglaciologic record and the conditions required to deposit them is not well understood, particularly for englacial eskers. We use uncrewed aerial vehicle data over weekly-to-annual timescales from 2021 to 2024 at Breiðamerkurjökull in Iceland to investigate how englacial eskers evolve after emerging from the glacier. During the study period, an esker emerged from an englacial conduit, experienced significant modification and was emplaced on the outwash plain at the edge of a proglacial lake. We find that englacial eskers experience significant erosion and modification as they interact with proglacial lakes or streams and their ice cores melt, implying that englacial eskers are not generally well preserved in the paleoglaciologic record. Both esker morphology and stratigraphy evolved over the study period, indicating that when observed in preserved englacial eskers, they do not necessarily reflect conduit emplacement conditions. Englacial eskers deposited at the edge of overdeepenings may be more likely to be preserved than those deposited elsewhere. Additionally, surface ice topography evolution is assessed to identify structural hazards at an esker-forming glacier margin, which is critical as glacial-related hazards increase in a warming climate.