Out-of-phase Late Pleistocene glacial maxima in the Western Alps reflect past changes in North Atlantic atmospheric circulation

Abstract Paleoglacier reconstructions in the northern and southern forelands of the European Alps indicate a synchronous Late Pleistocene glacial maximum during Marine Isotope Stage (MIS) 2, in phase with global ice volume records. However, strong controversy remains for the western foreland, where scarce and indirect dating as well as modeling studies suggest glacial maxima out of phase with the rest of the Alps. New luminescence dating brings the first direct Late Pleistocene glacial chronology for the western Alpine foreland and reveals two major glacier advances of similar maximum extent, at ca. 75–60 and ca. 40–30 ka, coinciding with MIS 4 and late MIS 3. We propose that asynchrony in glacial maxima between the western and the northern and southern Alpine forelands results from a progressive spatial reorganization of the atmospheric circulation over the North Atlantic in response to Northern Hemisphere ice-sheet fluctuations. While such a feedback mechanism has emerged from general circulation models, our Late Pleistocene paleoglacial reconstruction permits tracking of the spatiotemporal evolution of moisture advection patterns over Western Europe.