Global ice volume variations through the last glacial cycle simulated by a 3-D ice-dynamical model

Abstract

A coupled ice sheet—ice shelf—bedrock model was run at 20 km resolution to simulate the evolution of global ice cover during the last glacial cycle. The mass balance model uses monthly mean temperature and precipitation as input and incorporates the albedo—mass balance feedback. The model is forced by the GRIP and Vostok—derived temperature records (and by sea level and solar radiation variations), which are distributed spatially and seasonally. Model simulations show that at the last glacial maximum (LGM) a volume of ice representing about 65 m of sea level equivalent is stored on the Eurasian continent, whereas North America stores 42 m. The other regions (Greenland, Tibet, South-America and Antarctica) contribute about 17 m to global sea level lowering at the LGM compared to present day. Sensitivity experiments show that the ice volumes of the Eurasian and North American ice sheets are particularly sensitive to summer temperature changes. Finally, the timing and mechanism of grounded ice formation and expansion for the last glacial were studied for the Eurasian and North American continents. Ice sheet formation begins at 118 kyr BP in the Barents and Kara Sea region, over Baffin Island and in the high Cordilleran Range following a 4°C cooling. Alternating regions of ice sheet expansion by direct snowfall, ice flow and grounding of ice shelves can be identified. These relate to specific geomorphological traces, and may as such help in model validation.