Irvine, Calif., Jan. 25, 2021 – Scientists at the University of California, Irvine and NASA’s Jet Propulsion Laboratory for the first time have measured how the warming of coastal waters affects individual glaciers in fjords of Greenland. Their work is the subject of a recently published study in Advances in science.
Working under the auspices of the Oceans Melting Greenland mission for the past five years, the researchers used ships and planes to study 226 glaciers in every region of one of the largest islands on the Earth. They found that 74 glaciers were located in steep-walled valleys, accounting for nearly half of Greenland’s total ice loss between 1992 and 2017.
Such fjord-linked glaciers have been found to be the most controlled, a process by which warm, salty water at the base of the canyons melts the ice from below, causing the masses to collapse. separation faster than usual. In contrast, the team found that 51 glaciers in shallow gorges had fewer cuts and contributed only about 15 percent of the total ice loss.
“I was amazed by how lopsided it was. The largest and deepest glaciers are cut down much faster than the smallest glaciers in shallow fjords,” he said. lead author Michael Wood, a postdoctoral researcher at NASA’s Jet Dedication Laboratory in Southern California, began this research as a doctoral student at UCI. “In other words, the glaciers are the most sensitive to the warming waters and are the ones causing the loss of ice in Greenland.”
The study identified the dynamic where deeper fjords allow warmer ocean water to enter the shallower ones, speeding up the sinking process with some of the glaciers. largest streams in Greenland.
Greenland is home to one of the only two ice sheets on Earth, the largest of which is Antarctica. The ice in Greenland is more than two miles (three kilometers) thick in places. At the edges of the earth’s mass, the glaciers that extend out of the ice sheet travel slowly down valleys like frozen conveyor belts, which enter the fjords and then melts or breaks like icebergs. The ice is replenished with a drop of snow that has compressed over time into the ice pack.
If the ice sheet was in balance, the amount of snow accumulating on the roof would be roughly equal to the ice lost from melting, evacuation and calving – lumps breaking free from many anchors and going away to the sea.
But the ice sheet has been unbalanced since the 1990s. Melting has accelerated and calves have increased, causing glaciers that extend into the sea to return to land. Together, these are due to the decay of an ice sheet.
According to the research team, the buildup of warm salt water at the bottom of fjords was accelerated by a rise in temperature in the summer, which heats up the glacier surface, creating pools of melt water. This liquid seeps through cracks in the ice to create freshwater rivers that flow into the ocean where it interacts with salt water under fjords.
Glacier meltwater is salt-free, so it is lighter than sea water and rises to the surface like a plug, pulling up warm water and putting it in contact with a glacier mountain. Fjord depths are highly variable, but climate warming has a significant effect on other factors such as seawater temperatures and the amount of meltwater from glacier surfaces. All three factors combine to cause an accelerated decline of Greenland’s ice sheet, the researchers said.
As water temperatures around the Greenland coast are expected to rise in the future, these findings suggest that some climate models may underestimate the loss of ice- ice. flowing by at least a factor of two if they do not account for cutting down by a warm ocean.
The study also gives an insight into why many of Greenland’s glaciers never recovered after sudden ocean warming between 1998 and 2007, which caused a rise in near-ocean temperatures. 2 degrees Celsius. Although warming of the sea stopped between 2008 and 2017, glaciers had been so scarce in the previous decade that they continued to recover at an accelerated rate.
“We have known for more than a decade that warmer oceans play a major role in the evolution of Greenland’s glaciers,” said OMG deputy chief surveyor Eric Rignot, also of JPL and UCI. But for the first time, we have been able to quantify the mitigating impact and its greatest impact on glacier retreat over the last 20 years. . “
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In addition to funding from NASA, this research was supported by the National Science Foundation, the Dutch Center for Earth System Science, the Dutch Institute for Scientific Research and the French National Research Agency.
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