Evolution of the Antarctic ice sheet throughout the last deglaciation: A study with a new coupled climate—north and south hemisphere ice sheet model

Abstract

The aim of this paper is to assess, through the understanding of deglaciation processes, the contribution of the Antarctic ice sheet to sea-level rise during the last deglaciation. To achieve this goal, we use an Earth System model in which the interactions between the atmosphere, the ocean, the vegetation and the northern and Antarctic ice sheets are represented. This new tool allows the simulation of the evolution of the Antarctic ice volume, which starts to decrease at around 15 ka. At the end of deglaciation, the melting of the Antarctic ice sheet contributes to an ice-equivalent sea-level rise of 9.5 m in the standard experiment and 17.5 m in a more realistic sensitivity experiment accounting for a different bathymetry in the Weddell Sea which succeeds in producing both major ice shelves (Ross and Ronne-Filchner). In both experiments, the melting of all ice sheets contributes to 121.5 m and 129.5 m, respectively, which is very consistent with data. The new coupled model provides a timing and amplitude of the Antarctic deglaciation different from those previously obtained by prescribing the temperature record from the Vostok Antarctic ice core (78°27′S 106°52′E) as a uniform temperature forcing. Sensitivity experiments have also been performed to analyse the impact of the parameters at the origin of the deglaciation process: insolation changes, atmospheric CO 2 variation, basal melting and sea-level rise. All those parameters have an influence on the timing of the deglaciation. The prescribed global sea level rise is shown to be a major forcing factor for the evolution of the Antarctic ice volume during the last deglaciation. We quantify the direct effect of the sea-level rise due to the northern hemisphere ice sheet melting on the grounding line retreat which, in turn, favours enhancement of grounded ice flow by lowering the buttressing effect of ice shelves.