The sudden retreat of Patagonian glaciers 21,000 years ago cut off the supply of atmospheric dust to Antarctica, suggests a paper online this week in Nature Geoscience. Until now, the cause of the abrupt decline in dust in Antarctic ice cores was not understood, as it precedes any recognizable changes in Antarctic temperature or precipitation.

David Sugden and colleagues used radioisotopes to reconstruct the history of glaciers in the Tierra del Fuego region of Patagonia for the past 80,000 years. They found that the glaciers began to retreat 21,000 years ago ― the same time as dust levels in Antarctic ice cores dropped off. The team suggests that when the glaciers were at their maximum extent, they were delivering sediment to areas where it could be mobilized as dust and transported to Antarctica. When the glaciers retreated, the sediment was instead trapped in lakes in Patagonia.