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

• Main Authors: Kazmierczak, Elise, Sun, Sainan, Coulon, Violaine, Pattyn, Frank
• Format: Text
• Language: English
• Published: 2022
• Subjects: Antarctic; The Antarctic; Weertman; Antarc*; Ice Sheet; Ice Shelves
• Online Access: https://doi.org/10.5194/tc-2022-53; https://tc.copernicus.org/preprints/tc-2022-53/

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 classical 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 above slip laws is evaluated for the Antarctic ice sheet in two types of experiments, i.e., (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 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, 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 modulates basal sliding for a given power. In particular, subglacial models depending on subglacial water pressure decrease effective pressure significantly near the grounding line, leading to an increased sensitivity for a given power in the sliding law.