The role of shallow banks and marine ice domes in marine-based ice-sheet deglaciation

Abstract

Marine-based ice sheets are susceptible to collapse and faster retreat than their land-terminating counterparts. One of the key factors contributing to the relative stability of marine-terminating ice sheets is the presence of shallow bathymetric banks and islands acting as pinning points for the ice sheet. This study examines the seabed geomorphology of Storbanken, a shallow bank in the central Barents Sea. The preserved geomorphology/bedforms visible in the bathymetry provide new insights into the dynamics of the palaeo-Svalbard Barents Sea Ice Sheet (SBSIS). Contrary to previous assumptions that ice rises are transient features within ice shelves, the findings suggest that the Storbakken marine ice dome was a persistent ice accumulation centre that probably detached from the SBSIS after the collapse of its divide at ∼14–15 ka and before the ice cap was confined mainly to Svalbard area ∼12 ka. The geomorphic imprint left on the seabed reveals evidence for active deglaciation and the reorganization of multiple small ice streams, responding to shifts in driving stress within the marine ice dome. This challenges traditional models of gradual ice margin retreat and suggests that smaller marine ice domes and rises may have been more common during the deglaciation than previously recognized. Additionally, the study highlights discrepancies between empirical observations and existing ice-sheet reconstructions, which typically depict a stepwise ice-margin retreat without considering the formation of independent ice rises. The findings underscore the need to reevaluate the role of shallow bathymetric banks in influencing the stability and decay of marine-based ice sheets, with concomitant implications for understanding ice-sheet behaviour under future climate scenarios, which is particularly relevant for the chiefly marine-based West Antarctic Ice Sheet.