Ice sheet influence on atmospheric circulation explains the patterns of Pleistocene alpine glacier records in North America
Tulenko, Joseph P.
Briner, Jason P.
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We explore the hypothesis that the relative size of Pleistocene ice sheets in North America modulated regional climate and alpine glaciation. We compare Pleistocene alpine glacier chronologies across North America with a comprehensive general circulation model using reconstructed ice sheet extents at peak glacial conditions during Marine Isotope Stage (MIS) 2 and MIS 4. The effect of continent-wide ice sheets on atmospheric circulation during MIS 2 led to warming in Beringia and cooling in the western US; less expansive ice sheets during MIS 4 resulted in weaker ice sheet modulation of atmospheric circulation. This led to preservation of MIS 4 moraines in Beringia due to limited MIS 2 glaciation (resulting in a MIS 2/4 moraine sequence) and overriding of MIS 4 moraines – for sites with existing chronologies – in the western United States during MIS 2 (resulting in a MIS 2/6 moraine sequence). Our results highlight how influential ice sheets are for regional climate conditions.