Simulations of the Last Glacial Maximum ice sheet surface climate: Implications for the interpretation of ice core air content

Abstract

This paper reports on analyses of the surface pressure, surface wind, and seasonality of temperature and precipitation in the central parts of Greenland and Antarctica as simulated by different general circulation models (GCMs) for the present and for the Last Glacial Maximum (LGM) climates. These parameters, in addition to the mean surface temperature, influence the air content of the ice either directly or through their influence on the pore volume. To correctly interpret the air content of the ice in terms of past ice sheet elevation changes, the variations of these parameters must therefore be known. Most of the simulations discussed here have been carried out within the framework of the Paleoclimate Modeling Intercomparison Project. Moreover, a stretched grid GCM has been used with a high resolution over the ice sheets. We show that not taking into account changes of surface pressure at constant altitude between the LGM and today leads to an overestimation of past ice sheet elevation up to 150 m, while wind speed changes are too weak to have a significant influence on ice core air content. The results concerning changes of the amplitude or phase of the seasonal variations of precipitation and temperature are somewhat ambiguous. Most, but not all, of the models suggest an intensification of the seasonal cycle of surface temperatures over central Greenland, and, to a lesser extent, over central East Antarctica. Neglecting these changes might lead to an underestimation of past elevation by up to 140 m for the Greenland ice sheet, but this number is subject to large uncertainties.