Report

Freshwater Outburst from Lake Superior As a Trigger for the Cold Event 9300 Years Ago

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Science  29 Apr 2010:
1187860
DOI: 10.1126/science.1187860

Abstract

Paleoclimate proxy records reveal a pervasive cooling event with a Northern Hemispheric extent ~9300 years ago. Coeval changes in oceanic circulation of the North Atlantic imply freshwater forcing. However, the source, magnitude, and routing of meltwater remain unknown. Located in central North America, Lake Superior is a key site for regulating the outflow of glacial meltwater to the oceans. Here, we show evidence for a ~45 m rapid lake-level fall in this basin centered on 9300 calibrated years before present due to failure of a glacial drift dam on the southeast corner of the lake. We ascribe the widespread climate anomaly ~9300 years ago to this freshwater outburst delivered to the North Atlantic Ocean through Lake Huron–North Bay–Ottawa River–St. Lawrence River valleys.