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Bad News for Florida: Models of Greenland Ice Melting Could Be Way Off

Image: Water courses through Greenland's ice sheet during the summer melt

Water courses through Greenland's ice sheet during the summer melt on July 17, 2013. Joe Raedle / Getty Images

Existing computer models may be severely underestimating the risk to Greenland's ice sheet — which would add 20 feet to sea levels if it all melted — from warming temperatures, according to two studies released Monday.

Satellite data were instrumental for both studies — one which concludes that Greenland is likely to see many more lakes that speed up melt, and the other which better tracks large glaciers all around Earth's largest island.

The lakes study, published in the peer-reviewed Nature Climate Change, found that what are called "supraglacial lakes" have been migrating inland since the 1970s as temperatures warm, and could double on Greenland by 2060.

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The study upends models used by the Intergovernmental Panel on Climate Change because they "didn't allow for lake spreading, so the work has to be done again," study co-author Andrew Shepherd, director of Britain's Centre for Polar Observation and Modelling, told NBCNews.com.

Those lakes can speed up ice loss since, being darker than the white ice, they can absorb more of the sun's heat and cause melting. The melt itself creates channels through the ice sheet to weaken it further, sending ice off the sheet and into the ocean.

"When you pour pancake batter into a pan, if it rushes quickly to the edges of the pan, you end up with a thin pancake," study lead author Amber Leeson, a researcher at Britain's University of Leeds, explained in a statement. "It's similar to what happens with ice sheets: The faster it flows, the thinner it will be.

"When the ice sheet is thinner," she added, "it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet."

The mix of IPCC models have Greenland contributing 8.7 inches to global sea level rise by 2100 without the doubling of supraglacial lakes, but the team fears that a doubling could add almost as much as that over the next century.

Such a rise in sea level would have serious repercussions for heavily populated low-lying areas, like Florida or Bangladesh, which could see beach and barrier island erosion and salt water encroachment, scientists say.

The glaciers study, published in the peer-reviewed Proceedings of the National Academy of Sciences, used NASA satellite data to reconstruct how the height of the ice sheet has changed at nearly 100,000 locations from 1993 to 2012.

The team found significant variations that aren't factored in by existing computer models for future changes on Greenland because they focus on just four glaciers.

"The problem is that these models have been applied to four glaciers only, one of which has not been changing much, to predict how these glaciers may change in the future," Kees van der Veen, a study co-author and University of Kansas geographer, told NBCNews.com.

"Results for these four glaciers have been extrapolated to the entire ice sheet to estimate the contribution of the entire ice sheet to sea level rise," he adds. "Our results show that this is not appropriate because of how differently individual glaciers have changed over the last decade."

Image: Surface of the Greenland ice sheet
The surface of the Greenland ice sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. Beata Csatho

For example, those models don't account for rapid shrinkage in southeast Greenland, leading the researchers to believe the ice sheet could lose ice faster in the future than today's simulations would suggest.

The ice sheet has 242 outlet glaciers at least a mile wide, adds study lead author and University of Buffalo geophysicist Bea Csatho. "What we see is that their behavior is complex in space and time … The current models do not address this complexity."

Factors that might influence the differences include local variables like the width and depth of a glacier, how close it is to the water, the ocean floor's geology and even volcanic activity below ground, Csatho told NBCNews.com.

Ted Scambos, a senior scientist at the NASA and National Science Foundation funded National Snow & Ice Data Center, said the study provides "unprecedented detail" about Greenland.

"What Dr. Csatho's group has done," he said, "is truly admirable — marshaling a huge amount of data to reveal not just where, but when and how much, ice is being lost from every glacier system in Greenland."

Neither study tried to predict how far off current models might be, and both teams said it's up to modelers to now incorporate their data to come up with new estimates.

"It shouldn't be too difficult for modelers … so I would expect an advance pretty soon," Shepherd said. "It's a good example of why we need to consider observations and small-scale processes as well as running global climate models; you can never be sure that all factors have been accounted for."

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