High-resolution simulation of the Climate Change during the Last Glacial Maximum

Abstract

This study explores the response of climate features to the imposition of LGM conditions. The simulations were performed with the NCAR CCM3. The LGM conditions include a reduction in CO2 concentration, ice sheet topography, changes in land boundaries, and changes to orbital parameters. The lower boundary is fixed with specified sea surface temperatures (SST). The LGM SSTs and sea ice distributions are from climatologically averaged monthly data prepared with the August and February reconstructions by CLIMAP (1981). The LGM SSTs are lowered everywhere by 1°C. With LGM conditions, the largest surface cooling is found over the northern North Atlantic and the Southern Ocean and is associated with the increase in sea ice and higher surface albedo. The second largest cooling is found over the Laurentide ice sheet. In these regions the short-wave heat flux acts to cool the surface while the long-wave heat flux acts to warm the surface. The large surface cooling in the northern North Atlantic leads to a reduction in evaporation and thus a reduction in latent heat fluxes. Over land the large cooling of more than 12°C is found along the eastern margins of North America and Asia, and is consistent with paleo proxy records (e.g., Farrera et al., 1999). In conclusion the high-resolution climate model captures detailed climate features which have not been reproduced in lower-resolution models. This is particularly the case over land associated with a detailed representation of topography.