Reply on RC1

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The last deglaciation (21000 to 8000 years BP) of the Eurasian ice sheet (EIS), is thought to have been responsible for a sea level rise of about 20 meters. While many studies have examined the timing and rate of the EIS retreat during this period, many questions remain about the key processes that triggered the EIS deglaciation 21,000 years ago. Due to its large marine-based parts in the Barents-Kara and British Isles sectors, EIS is often considered as a potential analog of the current West Antarctic ice sheet (WAIS). Identifying the mechanisms that drove the EIS evolution might provide a better understanding of the processes at play in the West Antarctic destabilization. To investigate the relative impact of key drivers on the EIS destabilization we used the three-dimensional ice sheet model GRISLI (version 2.0) forced by climatic fields from five PMIP3/PMIP4 LGM simulations. In this study, we performed sensitivity experiments to test the response of the simulated Eurasian ice sheets to surface climate, oceanic temperatures (and thus basal melting under floating ice tongues) and sea level perturbations. Our results highlight that the EIS retreat is primarily triggered by atmospheric warming. Increased atmospheric temperatures further amplify the sensitivity of the ice sheets to sub-shelf melting. These results contradict those of previous modelling studies mentioning the central role of basal melting on the deglaciation of the marine-based Barents-Kara ice sheet. However, we argue that the differences with previous works are mainly related to differences in the methodology followed to generate the initial LGM ice sheet. We conclude that being primarily sensitive to the atmospheric forcing, the Eurasian ice sheet cannot be considered as a direct analogue of the present-day West Antarctic ice sheet. However, because of the expected rise in atmospheric temperatures, risk of hydrofracturing is increasing and could ultimately put the WAIS in a configuration similar to the pas Eurasian ice sheet.