There's a literal cloud hanging over the rapidly melting Greenland ice sheet. That's because a new study published Tuesday in Nature Communications reveals exactly how clouds are exacerbating the problem. Cloud cover over the ice sheet causes 56 billion tons of meltwater runoff every year, up to a third more than clear skies, Science Daily reports. But researchers were surprised to discover exactly how clouds are affecting the ice sheet, according to the study. Rather than trapping heat and causing ice to melt themselves, clouds do more damage by keeping temperatures warm at night and preventing the ice that melted during the day from refreezing, Phys.org reports. According to the Washington Post, 58% of meltwater refreezes under clear skies. That drops to 45% when it's cloudy.
All this is important because the Greenland ice sheet is the second largest in the world and is causing nearly one-third of rising sea levels globally, Phys.org reports. "Over the next 80 years, we could be dealing with another foot of sea level rise around the world," study co-author Tristan L'Ecuyer says. "Parts of Miami and New York City are less than two feet above sea level; another foot of sea level rise and suddenly you have water in the city." Even worse, climate change may be increasing cloud cover over Greenland, leading to more melting, according to the Post. But this new study is a good step toward understanding how bad things could get. "This is something we have to get right if we want to predict the future," Phys.org quotes L'Ecuyer. (The last stable piece of the Greenland Ice Sheet is no longer stable.)