Modeling the present and last glacial maximum transportation of dust to the arctic with an extended source scheme

Ice core studies indicate that rates of deposition of mineral dust at the surface of polar ice sheets were much larger during the last ice age than at present (Thompson, 1977, Hammer et al., 1985, Legrand el al., 1988). Attempts to reproduce this observation using models of the atmospheric dust cycle imbedded within general circulation models of the atmosphere ((A)GCM's) have been unsuccessful so far (Genthon, 1992,;Joussaume, 1993). The origin of this systematic failure can be traced in a poor definition of the sources, an insufficient quality of the atmospheric cycle simulated by the GCM's, an inadequate modeling of aerosol processes or (likely) a combination of these.We here present a new source formulation for modeling the atmospheric dust cycle and particularly the transportation of dust to the Arctic. Due to the scarce information on soil properties and vegetation for previous times we chose a formulation that uses a prescribed vegetation cover with physical restrictions inferred from the simulated climate.With this approach some features of the present dust cycle are reproduced reasonably well, but although dust production from the major deserts is somewhat enhanced for the ice age simulation it, too, fails to simulate the ice age increase of the dust in the Arctic.