Climate and biogeochemical response to a rapid melting of the West Antarctic Ice Sheet during interglacials and implications for future climate

We study the effects of a massive meltwater discharge from the West Antarctic Ice Sheet (WAIS) during interglacials onto the global climate-carbon cycle system using the Earth system model of intermediate complexity LOVECLIM. Prescribing a meltwater pulse in the Southern Ocean that mimics a rapid disintegration of the WAIS, a substantial cooling of the Southern Ocean is simulated that is accompanied by an equatorward expansion of the sea ice margin and an intensification of the Southern Hemispheric Westerlies. The strong halocline around Antarctica leads to suppression of Antarctic Bottom Water (AABW) formation and to subsurface warming in areas where under present-day conditions AABW is formed. This subsurface warming at depths between 500 and 1500 m leads to a thermal weathering of the WAIS grounding line and provides a positive feedback that accelerates the meltdown of the WAIS. Our model results further demonstrate that in response to the massive expansion of sea ice, marine productivity in the Southern Ocean reduces significantly. A retreat of the WAIS, however, does not lead to any significant changes in atmospheric CO2. The climate signature of a WAIS collapse is structurally consistent with available paleoproxy signals of the last interglacial MIS5e.