Subglacial hydrology modulates basal sliding response of the Antarctic ice sheet to climate forcing

Abstract

Abstract. Major uncertainties in the response of ice sheets to environmental forcing are due to subglacial processes. These processes pertain to the type of sliding or friction law as well as the spatial and temporal evolution of the effective pressure at the base of ice sheets. We evaluate the classic Weertman–Budd sliding law for different power exponents (viscous to near plastic) and for different representations of effective pressure at the base of the ice sheet, commonly used for hard and soft beds. The sensitivity of the above slip laws is evaluated for the Antarctic ice sheet in two types of experiments: (i) the ABUMIP experiments in which ice shelves are instantaneously removed, leading to rapid grounding-line retreat and ice sheet collapse, and (ii) the ISMIP6 experiments with realistic ocean and atmosphere forcings for different Representative Concentration Pathway (RCP) scenarios. Results confirm earlier work that the power in the sliding law is the most determining factor in the sensitivity of the ice sheet to climatic forcing, where a higher power in the sliding law leads to increased mass loss for a given forcing. Here we show that spatial and temporal changes in water pressure or water flux at the base modulate basal sliding for a given power, especially for high-end scenarios, such as ABUMIP. In particular, subglacial models depending on subglacial water pressure decrease effective pressure significantly near the grounding line, leading to an increased sensitivity to climatic forcing for a given power in the sliding law. This dependency is, however, less clear under realistic forcing scenarios (ISMIP6).

A framework for time-dependent Ice Sheet Uncertainty Quantification, applied to three West Antarctic ice streams

“…In previous configurations we use the Weertman-Budd sliding law, but due to the sensitivity of the time-dependent ice sheet model to the choice of sliding law (Brondex et al, 2019;Kazmierczak et al, 2022;Barnes and Gudmundsson, 2022) we trial our error propagation framework using the Cornford law and compare qualitative differences from both laws in Fig 10 . We use the same velocity constraints (i.e. same as in Sect.…”

Sediment Freeze‐On and Transport Near the Onset of a Fast‐Flowing Glacier in East Antarctica

“…While surface processes of the AIS are relatively convenient to study, the processes at the ice base remain challenging to investigate due to their inaccessibility. However, a better understanding of the physical conditions, material properties, and mechanical processes at the ice‐bed interface, such as basal ice temperature, subglacial hydrology, and basal sliding (Dawson et al., 2022; Kazmierczak et al., 2022; Pollard & DeConto, 2012), are critical factors influencing ice‐sheet configuration and ice flow (Pattyn, 2010). Airborne geophysical methods like radar give us insight into the englacial and subglacial processes.…”

Inferring the Basal Friction Law From Long Term Changes of Glacier Length, Thickness and Velocity on an Alpine Glacier

“…Whereas the form of the Glen's law is widely accepted to be a power law with an exponent n typically considered to be equal to 3 (Cuffey & Paterson, 2010), the friction law can take various forms and its nonlinearity is not well established (Gimbert, Gilbert, et al., 2021; Zoet & Iverson, 2020). This leads to large uncertainty when estimating the evolution of ice sheets and glaciers over a long time scale (e.g., Brondex et al., 2019; Bulthuis et al., 2019; Gladstone et al., 2017; Kazmierczak et al., 2022; Ritz et al., 2015).…”