Influence of Patagonian glaciers on Antarctic dust deposition during the last glacial period

Abstract

Dust in the atmosphere plays a role in the transparency of the atmosphere1, the mineral nourishment of the oceans and can be used to constrain global circulation models today and in the past. Antarctic ice cores provide an 800,000 year record of changes in dust flux thought to reflect changes in the vigour of global atmospheric circulation and environmental conditions in source areas. Here for the first time we link the source of Last Glacial dust peaks in Antarctica to the gravel outwash plains of Patagonian glaciers in the Magellan area of southernmost South America. We find that there is an on-off switch in that the peaks coincide with episodes when glaciers discharge sediment directly onto outwash plains but not when they terminate in lakes. This finding helps solve several long-standing puzzles, namely: why both dust and fresh water diatom concentrations during glacial maxima are so much higher (x ~20) than at the present day; why dust peaks occur only below a certain temperature threshold; and why the decline in dust concentrations at the end of glacial cycles precedes the main phase of warming, the rise in sea level, and the reduction in southern hemisphere sea ice extent.