Impact of the North American ice-sheet orography on the Last Glacial Maximum eddies and snowfall

The present work evaluates the influence of the North American ice-sheet orography on the Last Glacial Maximum (LGM, 21,000 years ago) atmospheric circulation and snowfall in the northern mid-latitudes, focusing on the North Atlantic sector. Three Atmospheric General Circulation Model experiments are analysed: a control and an LGM climate simulation, and an LGM run with flat ice-sheets over northern North America. This ice-sheet orography affects lee-cyclogenesis over North America and forces differences in stationary waves and therefore in the baroclinicity of the mean how. As a result, the Atlantic storm-track is reinforced in the flat ice-sheet experiment compared to the LGM one. This, in turn, has a profound impact on snowfall over northern Europe, implying a coupling between the two ice-sheets.