Glacial-interglacial variations of meridional transport and washout of dust: a one-dimensional model

Abstract

Measurements of insoluble dust in the Greenland Ice Core Project ice core reveal that the concentration of dust is about 100 times higher in ice from the last glacial maximum than it is today. In order to understand the glacial climate it is of importance to establish to what extent this increased level was due to changes in the source areas and to what extent it was due to changes in the atmospheric tramsportation. We here present a one-dimensional model evaluating the effect of changes in the zonally averaged atmospheric circulation on the atmospheric hydrological cycle and dust transportation. The main characteristics of the altered climate during glacial periods are assumed to be increased baroclinicity, an equatorward displacement of the baroclinic zone, and reduced evaporation. The model reproducez the zonally averaged hydrological cycle of the present climate reasonably well, and it produces a halving of snow accumulation in polar areas for glacial periods. From the ice core data we obtain a power law dependence between the concentration of dust in the ice and the accumulation related to long-term climate variations. With the input of dust to the atmosphere being independent of the simulated climate, the model reproduces this power law. The obtained power is strongly dependent on the assumed position of the dust sources. For reasonable estimates of the present-day dust sources the simulated mechanism may account for a twofold to sixfold increase in dust concentration in polar ice from interglacial to full glacial conditions. Concurrently, the atmospheric content of dust is increased at all latitudes during the glacial period.