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Scientists Find an Unexpected Factor that Could be Driving Greenland’s Ice Loss: Cloud Cover

There’s been another breakthrough in the study of the Greenland ice sheet, whose increasing melt rate and growing contribution to global sea-level rise has captured the attention and concern of climate scientists in recent years. While changes in air temperature, water temperature and precipitation are known to influence melting events on the ice sheet, a new study has identified another, perhaps less obvious culprit: clouds.

It’s a finding that should be reflected in current climate models to help scientists make more accurate predictions about future Greenland melt — and could become even more important in the coming years if cloud cover over the ice sheet were to increase as a result of climate change.

The study, published Tuesday in the journal Nature Communications, concludes that cloud cover can actually increase the amount of meltwater that runs off the surface of the glacier. Clouds have the effect of trapping heat on Earth; they can cause local temperatures to be warmer, so one would imagine that clouds might increase the amount of ice that actually melts during the day. But it turns out that the influence of cloud cover is strongest after the sun goes down. At night, the clouds actually prevent temperatures from cooling as much as they would on clear nights and keep already-melted ice from refreezing. This liquid water then pools on the surface of the ice and can be lost as runoff.

Don Greene

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