By Sid Perkins
About 90,000 years ago, an ice sheet blocked the flow of rivers in northern Russia, leading to the formation of massive lakes. New computer models suggest that those frigid bodies of water significantly cooled the region in summer months. That change in the local climate, in turn, allowed the massive ice sheet to expand more quickly than if the lakes had never formed.
At their largest, the lakes covered an area more than three times the size of North America’s five Great Lakes, says Martin Jakobsson, a marine geologist at the University of New Hampshire in Durham.