Glaciers and ice sheets at both ends of Earth are melting ever more quickly from below due to warmer ocean waters, advancing sometimes in enormous earth-shaking "jolts," new research has found.
Scientists have already determined that Greenland's and Antarctica's glaciers have melted at accelerating rates because of warmer air temperatures. But in findings published today in the journal Science, researchers have presented new evidence that warmer ocean temperatures also melt the glaciers from below.
"There is a big temperature contrast between the warm ocean water and the cold ice, and melting occurs at a very rapid rate," said Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center and author of the study. "The melting reduces the friction that holds these glaciers back, allowing them to accelerate."
That increased acceleration has led to an increasing frequency of "glacial earthquakes," according to a separate paper also in Science.
The number of glacial earthquakes has doubled in the past five years as ice sheets respond to a warming climate, according to a team led by Harvard University researcher Göran Ekström. Most of the earthquakes occur in late summer.
"People often think of glaciers as inert and slow moving, but in fact they can also move rather quickly," Ekström said in a statement. "Some of Greenland's glaciers, as large as Manhattan and as tall as the Empire State Building, can move 10 meters in less than a minute, a jolt that is sufficient to generate moderate seismic waves."
To Ekström, the reason behind all the increased glacier activity is clear.
"I think it is very hard not to associate this with global warming," he said.
Bindschadler, who spoke with reporters on a conference call, said his new findings are consistent with other recent research that shows Greenland and Antarctica melting faster, also because of global warming.
In early March, scientists reported that Greenland's glaciers moved at twice their expected speed, up to 120 feet per day, which has nearly doubled the amount of fresh water being dumped into the ocean in only five years.
"I think what's going to happen in the future is a continued acceleration of sea level rise," Bindschadler said. "The rate is going to increase and the magnitude is going to increase. And that's what alarms me about this."
Bindschadler said he is working to better understand the processes at work so that scientists can better predict what will happen with some degree of certainty.
"But this does not comfort me in my view of the future," he said.