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Watching the River Flow

Meltwater rushes in a stream across the top of the Greenland Ice Sheet in July 2007. Thousands of lakes form every summer on top of Greenland’s glaciers, as sunlight and warm air melt ice on the surface. Fast moving horizontal streams move water into and out of the lakes, but glaciologists like Sarah Das are more interested in the vertical flows that take water from the top of the ice to the bottom, lifting and lubricating the moving sheet. Das and colleagues will visit Greenland in July to continue their studies. (Photo by Sarah Das, Woods Hole Oceanographic Institution)