Forty years of satellite imagery reveal that meltwater lakes on the marginof the Greenland Ice Sheet have expanded substantially inland to higherelevations with warming. These lakes are important because they provide amechanism for bringing water to the ice bed, causing sliding. Inlandexpansion of lakes could accelerate ice flow by bringing water to previouslyfrozen bed, potentially increasing future rates of mass loss. Increasinglake elevations closely follow the rise of the mass balance equilibrium lineover much of the ice sheet, suggesting no physical limit on lake expansion.Data are not yet available to detect a corresponding change in ice flow, andthe potential effects of lake expansion on ice sheet dynamics are notincluded in ice sheet models.
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