Constraining the glacier basal friction law from multidecadal to century scales observations of surface velocity and thickness changes on Alpine glaciers
Year: 2026
Type: preprint
Abstract: Although basal sliding governs the dynamics of glaciers and ice sheets, it is controlled by poorly constrained processes linked to subglacial hydrology. Here, we combine a unique dataset of surface velocity and thickness changes spanning multidecadal to century-scale observations from eight Alpine glaciers with full-Stokes modeling to derive relationships between basal sliding velocities and basal shear stresses. Our analysis shows that changes in basal friction across hard-bedded sites can be described within a single framework of stress-bounded friction law in which the average basal effective pressure is constant over time but varies from site to site. Basal stress is generally found to be close to its upper bound, leading to a strong sliding velocity response to minor changes in shear stress in the 1920s and 1980s when the glaciers experienced positive mass balance. During the recent deglaciation, bed shear stress tends to align on the classical Weertman power law relationship with an exponent of 3. We suggest that constant effective pressure may occur as a result of channel-like conduits controlling winter drainage through establishing connections across basal cavities in the absence of surface melt input. This hypothesis is also supported by our observation that average basal effective pressure depends on surface slope, which is to be expected given that pressure in steady channel is function of hydraulic potential gradients. This study provides observational constraints on basal friction laws and their parameter values that can directly be used for glacier and ice-sheet modeling.
Source: HAL
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7135158285