Warming Greenland Ice Sheet Passes Level of No Return

Even when the local weather cools, examine finds, glaciers will proceed to shrink.

Practically 40 years of satellite tv for pc information from Greenland exhibits that glaciers on the island have shrunk a lot that even when world warming had been to cease at this time, the ice sheet would proceed shrinking.

The discovering, revealed at this time, Aug. 13, within the journal Communications Earth and Atmosphere, implies that Greenland’s glaciers have handed a tipping level of kinds, the place the snowfall that replenishes the ice sheet every year can not sustain with the ice that’s flowing into the ocean from glaciers.

“We’ve been taking a look at these distant sensing observations to check how ice discharge and accumulation have different,” mentioned Michalea King, lead creator of the examine and a researcher at The Ohio State College’s Byrd Polar and Local weather Analysis Heart. “And what we’ve discovered is that the ice that’s discharging into the ocean is much surpassing the snow that’s accumulating on the floor of the ice sheet.”

Icebergs close to Greenland kind from ice that has damaged off–or calved–from glaciers on the island. A brand new examine exhibits that the glaciers are shedding ice quickly sufficient that, even when world warming had been to cease, Greenland’s glaciers would proceed to shrink. Credit score: Picture courtesy Michalea King

King and different researchers analyzed month-to-month satellite tv for pc information from greater than 200 giant glaciers draining into the ocean round Greenland. Their observations present how a lot ice breaks off into icebergs or melts from the glaciers into the ocean. Additionally they present the quantity of snowfall every year—the way in which these glaciers get replenished.

The researchers discovered that, all through the 1980s and 90s, snow gained by means of accumulation and ice melted or calved from glaciers had been principally in steadiness, maintaining the ice sheet intact. By these many years, the researchers discovered, the ice sheets usually misplaced about 450 gigatons (about 450 billion tons) of ice every year from flowing outlet glaciers, which was changed with snowfall.

“We’re measuring the heart beat of the ice sheet—how a lot ice glaciers drain on the edges of the ice sheet—which will increase in the summertime. And what we see is that it was comparatively regular till a giant improve in ice discharging to the ocean throughout a brief five- to six-year interval,” King mentioned.

Michalea King

The researchers’ evaluation discovered that the baseline of that pulse—the quantity of ice being misplaced every year—began rising steadily round 2000, in order that the glaciers had been shedding about 500 gigatons every year. Snowfall didn’t improve on the similar time, and over the past decade, the speed of ice loss from glaciers has stayed about the identical—that means the ice sheet has been shedding ice extra quickly than it’s being replenished.

“Glaciers have been delicate to seasonal soften for so long as we’ve been in a position to observe it, with spikes in ice discharge in the summertime,” she mentioned. “However beginning in 2000, you begin superimposing that seasonal soften on the next baseline—so that you’re going to get much more losses.”

Earlier than 2000, the ice sheet would have about the identical probability to achieve or lose mass every year. Within the present local weather, the ice sheet will acquire mass in just one out of each 100 years.

King mentioned that giant glaciers throughout Greenland have retreated about three kilometers on common since 1985—“that’s a variety of distance,” she mentioned. The glaciers have shrunk again sufficient that lots of them are sitting in deeper water, that means extra ice is in touch with water. Heat ocean water melts glacier ice, and in addition makes it tough for the glaciers to develop again to their earlier positions.

That implies that even when people had been someway miraculously in a position to cease local weather change in its tracks, ice misplaced from glaciers draining ice to the ocean would doubtless nonetheless exceed ice gained from snow accumulation, and the ice sheet would proceed to shrink for a while.

“Glacier retreat has knocked the dynamics of the entire ice sheet into a relentless state of loss,” mentioned Ian Howat, a co-author on the paper, professor of earth sciences and distinguished college scholar at Ohio State. “Even when the local weather had been to remain the identical and even get a bit of colder, the ice sheet would nonetheless be shedding mass.”

Shrinking glaciers in Greenland are an issue for your entire planet. The ice that melts or breaks off from Greenland’s ice sheets leads to the Atlantic Ocean—and, finally, all the world’s oceans. Ice from Greenland is a number one contributor to sea degree rise—final 12 months, sufficient ice melted or broke off from the Greenland ice sheet to trigger the oceans to rise by 2.2 millimeters in simply two months.

The brand new findings are bleak, however King mentioned there are silver linings.

“It’s at all times a constructive factor to be taught extra about glacier environments, as a result of we are able to solely enhance our predictions for the way quickly issues will change sooner or later,” she mentioned. “And that may solely assist us with adaptation and mitigation methods. The extra we all know, the higher we are able to put together.”

Reference: “Dynamic ice loss from the Greenland Ice Sheet pushed by sustained glacier retreat” by Michalea D. King, Ian M. Howat, Salvatore G. Candela, Myoung J. Noh, Seonsgu Jeong, Brice P. Y. Noël, Michiel R. van den Broeke, Bert Wouters and Adelaide Negrete, 13 August 2020, Communications Earth and Atmosphere.
DOI: 10.1038/s43247-020-0001-2

This work was supported by grants from NASA. Different Ohio State researchers who labored on this examine are Salvatore Candela, Myoung Noh and Adelaide Negrete.