Watching flow sharpens picture of moving glaciers
It took almost a month for meltwater to accumulate atop Greenland’s ice sheet in the summer of 2006. It took only 90 minutes for all that water — a lake so large it could fill New Orleans’ Superdome more than 12 times over — to pour through a crack in the kilometer-thick ice below it and drain the lake dry.
At its height, the torrent exceeded that of Niagara Falls, and its rumbling triggered seismic instruments nearby. GPS equipment indicated that the westward flow of ice in the region briefly surged, a sign that the water drained down to the bedrock and temporarily lubricated the boundary between ice and rock.
Some scientists have suggested that an increased number of similar events could spur a collapse of much of Greenland’s islandwide ice sheet, leading to sudden rises in sea level. But new analyses hint that the overall effects of an increase in such subglacial lubrication, while possibly substantial, would not be cat