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Greenland ice sheet is melting more than it has in centuries, scientists say

Large rivers form on the surface of the ice sheet in summer, rapidly moving meltwater from the ice sheet to the ocean.
Large rivers form on the surface of the ice sheet in summer, rapidly moving meltwater from the ice sheet to the ocean.(Sarah Das/WHOI)

Scientists say the amount of meltwater running off of the Greenland ice sheet has increased in modern times because of climate change, and rapid increases could be ahead.

“Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than any time during the last three and a half centuries, if not thousands of years,” Luke Trusel, a glaciologist at Rowan University’s School of Earth & Environment and former postdoctoral scholar at Woods Hole Oceanographic Institution, said in a statement.

The increased melting began around the same time humans started altering the atmosphere in the mid-1800s, said Trusel, lead author of a study of the meltwater runoff that was published Wednesday in the journal Nature.

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“From a historical perspective, today’s melt rates are off the charts, and this study provides the evidence to prove this” Sarah Das, a glaciologist at Woods Hole Oceanographic Institution and coauthor of the study, said. “We found a 50 percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a 30 percent increase since the 20th century alone.”

The loss of ice from Greenland is one of the key drivers of rising global sea levels. Icebergs breaking off into the ocean from the edge of glaciers are a spectacular example. But more than half of water from the ice sheet that goes into the ocean comes from meltwater runoff, researchers said.

A meltwater stream on the ice sheet
A meltwater stream on the ice sheet(Sarah Das/WHOI)

“The magnitude of recent [Greenland ice sheet] melting is exceptional over at least the last 350 years,” the study said.

The scientists used ice core samples to look back into the history of melting on the ice sheet. They were able to go back as far as the 17th century.

Satellite methods to understand melting rates have only been around in recent decades, so the ability to go back further in time was important.

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A deep meltwater canyon on the ice sheet
A deep meltwater canyon on the ice sheet(Sarah Das/WHOI)
Another view of a meltwater canyon
Another view of a meltwater canyon(Sarah Das/WHOI)

The researchers warned that their findings also showed that it would only take a little additional warming to cause ice sheet melting to spike and sea levels to rise.

Because of a “nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in [Greenland ice sheet] runoff and sea-level contributions,” the study said.

“Warming means more today than it did in the past,” Trusel said in the statement.

Researchers from the MIT-WHO Joint Program, University of Washington, Wheaton College, University of Leige, Desert Research Institute, and Utrecht University also worked on the study.

Luke Trusel, lead author, examining an ice core sample
Luke Trusel, lead author, examining an ice core sample(Sarah Das/WHOI)