It's a bad week for ice. Last Tuesday, researchers announced that the East Antarctic Ice Sheet – which was previously considered stable or even growing – actually melted very quickly. And yesterday (January 21), a new study found that southwest Greenland – another area where ice should be safe – dumped more meltwater into the oceans than any other region on the ice island.
Both of these developments pose problems for coastal communities threatened by rising tides.
"We will see sea level rise faster and faster for the foreseeable future," Michael Bevis, lead author of the Greenland study, said in a statement. "Once you reach that critical point, the only question is: How severe is that?"
Greenland has long been a major source of concern for scientists who study sea level rise. But they used to think their biggest concern was the southeast and northwest, home to large glaciers that were destroyed into icebergs when it was too hot. The Bergs floated into the sea and melted, adding water to the ocean. On the other hand, Southwest Greenland does not have many glaciers, so it does not spawn many icebergs. But the Bevis team found that during the increasingly hot summers, the melting rivers that grew had flowed out from the southwest directly into the sea, accelerating the loss of ice. In 2012, Greenland melted four times faster than in 2003, according to the study, led by the loss of ice in the southwest that is said to be stable.
Ninety-seven percent of the surface of the Greenland ice sheet melts in 2012, the level of melting ice on the island has not been seen since 1889, according to Kaitlin Keegan, a Dartmouth research associate who studies Arctic ice. In a typical year, he said, summer temperatures were at a maximum of -14 ° C. But Keegan recalled the feeling of surrealism doing fieldwork at the center of the Greenland ice sheet in the summer of 2012, when temperatures rose above freezing. "When the wind is still light, you can go outside wearing a shirt," he said.
It is not clear exactly how much melt water from unpredictable areas such as southwest Greenland must change our predictions for sea level rise. But researchers are not optimistic. "Sea level rise is a field of research in climate change where there are many things unknown," Keegan said. "But if you take the mass of ice from Greenland and put it directly into the sea at a speed faster than whoever models it, that would imply that sea level projections might be a little conservative."
"This is just another indication that these changes are not projections into the future or things to worry about about 20 years from now," said Eric Klein, a professor of geology at the University of Alaska, who was not involved with the study. "These changes are not far away – not in terms of time or space. If we lose the mass of ice from Greenland or Antarctica and the ocean rises, it will be felt globally, not only in the North Pole or Antarctica."