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article imageWarming Greenland ice sheet passes point of no return

By Karen Graham     Aug 14, 2020 in Environment
Nearly 40 years of satellite data from Greenland shows that glaciers on the island have shrunk so much that even if global warming were to stop today, the ice sheet would continue shrinking.
These finfings were published Thursday in the journal Nature Communications Earth and Environment, and suggests that Greenland's glaciers have reached a tipping point, or perhaps the point of no return.
This means that if the climate crisis were to end today, the ice sheet would continue to shrink because the amount of snow fall each year is less than the amount of melted ice flowing into the ocean each year.
“We’ve been looking at these remote sensing observations to study how ice discharge and accumulation have varied,” said Michalea King, lead author of the study and a researcher at The Ohio State University’s Byrd Polar and Climate Research Center.
"And what we've found is that the ice that's discharging into the ocean is far surpassing the snow that's accumulating on the surface of the ice sheet."
Jakobshavn Glacier in western Greenland is notorious for being the world’s fastest-moving glacier....
Jakobshavn Glacier in western Greenland is notorious for being the world’s fastest-moving glacier. It is also one of the most active, discharging a tremendous amount of ice from the Greenland Ice Sheet into Ilulissat Icefjord and adjacent Disko Bay—with implications for sea level rise. LandSat image dated June 18, 2019.
NASA Earth Observatort
The researchers analyzed monthly satellite data from more than 200 large glaciers draining into the ocean around Greenland, dating back to the 1980s and 1990s. Doing so, they were able to calculate how much ice crumbles into icebergs or seeps into the ocean, as well as track yearly snowfall amounts, according to Science Daily.
The team found that through the 1980s and 90s, ice loss and annual snowfall amounts were basically in balance, keeping the ice sheet intact. During those years, the Greenland ice sheet lost about 450 gigatons (about 450 billion tons) of ice each year from flowing outlet glaciers, which was replaced with snowfall.
“We are measuring the pulse of the ice sheet—how much ice glaciers drain at the edges of the ice sheet—which increases in the summer. And what we see is that it was relatively steady until a big increase in ice discharging to the ocean during a short five- to six-year period,” King said, reports the NY Daily News.
A large stream of meltwater (about 5 to 10 meters in width) emerges from an upstream supraglacial la...
A large stream of meltwater (about 5 to 10 meters in width) emerges from an upstream supraglacial lake in the Greenlandic ice on July, 21 2012, as seen from a helicopter by researcher Marco Tedesco. The darker shapes are minor streams covered by cryoconite (a mix of dust particles, soot, meteorite dust and organic material) which covers the ice sheet.
M. Tedesco/CCNY for NASA ICE
King points out that large glaciers across Greenland have retreated about 3 kilometers (1.9 miles) on average since 1985—“that’s a lot of distance,” she said. The glaciers have shrunk back enough that many of them are sitting in deeper water, meaning more ice is in contact with water. Warm ocean water melts glacier ice, and also makes it difficult for the glaciers to grow back to their previous positions.
“Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss,” said Ian Howat, a co-author on the paper, professor of earth sciences and distinguished university scholar at Ohio State. “Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass.”
Greenland's retreating glaciers and melting ice sheet are leading contributors to rising ocean levels. As a matter of fact, enough ice melted or broke off from the Greenland ice sheet last year to cause the oceans to rise by 2.2 millimeters in just two months.
This work was supported by grants from NASA. Other Ohio State researchers who worked on this study are Salvatore Candela, Myoung Noh and Adelaide Negrete.
More about Greenland, Ice sheet, glaciers retr4eating, point of no return, Global warming
 
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