A model study of the relation between Northern Hemisphere glaciation and precipitation rates

Abstract

In order to study the relation between ice cover and precipitation rates in the Northern Hemisphere, we have forced a zonal dynamical climate model by prescribing the degree of glaciation as a lower boundary condition. The model is a modified version of the one developed by 'SALTZMAN and VERNEKAR (1971). It includes a hydrological cycle and computes a zonally symmetric solution for summer and winter. We have found that if ice sheets grow to the south, the precipitation rate in the subtropics and the polar basin decreases, but in the latitude belt where the continental ice sheets are located it increases. This effect is due to en enhanced activity of baroclinic waves along the southern edge of the ice cover and a consequent increase of the poleward water vapour flux. If the ice cover extends south of 50 °N, the average precipitation rate over the ice sheet starts to decrease. These results are in agreement with the 'observational' fact that during full glacials the Northern Hemisphere continental ice sheets extend to about 50 °N.