Simulation of the last glacial inception and rapid ice sheet growth in the McGill Paleoclimate Model

Abstract

A two‐dimensional (2‐D) dynamic ice sheet model coupled to the McGill Paleoclimate Model (MPM) under Milankovitch forcing and Vostok‐derived atmospheric CO 2 levels is used to investigate the last glacial inception and subsequent rapid ice sheet growth in the Northern Hemisphere (NH). The impacts on ice sheet growth of the elevation effect of orography and the freezing of rain/refreezing of meltwater are evaluated. The results show that while Milankovitch forcing only is sufficient to initiate the formation of permanent North American and Eurasian ice at around 120 kyr BP, rapid ice sheet growth during the next 10 kyr only occurs when the above two processes and an active ocean component are included. The modelled ice volume‐equivalent drop in sea level during this growth period is estimated to be about two‐thirds of that found from sea level reconstructions. Finally, the ice sheet‐thermohaline circulation interactions and ice sheet thickness distribution are also investigated.