Reuters: Scientists were baffled last year after meltwater lakes atop Greenland's ice sheet suddenly drained out at rates rivaling Niagara Falls. Now a team of U.S. researchers says it has figured out the bizarre phenomenon and that could help them forecast global sea-level rise. Vertical shafts in the ice sheet, called moulins, can funnel melt water beneath parts of the glacier and lift them up. This causes cracks beneath the so-called supragalcial lakes that can empty them in days, according to scientists...