The Greenland and Antarctic ice sheets are now losing more than three times as much ice a year as they were 30 years ago, according to a comprehensive new international study.
Using 50 different satellite estimates, the researchers found that Greenland melting has accelerated in recent years. He Greenland’s average annual melt from 2017 to 2020 was 20% more annually than at the beginning of the decade and more than seven times greater than its annual shrinkage in the early 1990s.
The new figures “are really quite disastroussaid study co-author Ruth Mottram, a climate scientist at the Danish Meteorological Institute. “We are losing more and more ice from Greenland.”
The study’s lead author, Ines Otosaka, a glaciologist at the University of Leeds in the United Kingdom, said that accelerated ice sheet loss is clearly caused by human-caused climate change.
From 1992 to 1996, the two ice sheets, which contain 99% of the world’s freshwater ice, shrank by 116 billion tons (105 billion metric tons) a year, two-thirds of Antarctica.
But from 2017 to 2020According to the most recent data available, combined melt soared to 410 billion tons (372 billion metric tons) a year, more than two-thirds of Greenlandthe study said in the journal Earth System Science Data on Thursday .
“This is one devastating trajectorysaid US National Snow and Ice Center deputy principal scientist Twila Moon, who was not part of the study. “These rates of ice loss are unprecedented during modern civilization.”
Since 1992, Earth has lost 8.3 trillion tons (7.6 trillion metric tons) of ice from the two ice sheets., the study found. That’s enough to inundate the entire United States with 33.6 inches (almost 0.9 meters) of water or submerge France in 49 feet (almost 15 meters).
But because the world’s oceans are so large, the melting of ice sheets since 1992 only adds up to just under an inch (21 millimeters) of sea level rise, on average. Worldwide, sea level rise is accelerating and the melting of ice sheets has gone from contributing 5% of sea level rise to now accounting for more than a quarter, according to the study. The rest of the sea rise comes from the expansion of warmer water and the melting of glaciers.
A team of more than 65 scientists regularly calculates ice sheet loss in research funded by NASA and the European Space Agency, and Thursday’s study adds three more years of data. They use 17 different satellite missions and examine ice sheet melt in three different techniques, Otosaka said, and all the satellites, radar, ground observations and computer simulations basically say the same thing: melting of the ice sheet is accelerating.
Greenland between 2017 and 2020 averaged about 283 billion tons (257 billion metric tons) of melt per year, compared to just 235 billion tons (213 billion metric tons) annually between 2012 and 2016.
The latest figures also showed what appears to be a slowdown in melting in parts of Antarctica, which has much more ice than Greenland. That’s mostly due to smaller, more fleeting climate changes and the overall long-term trend still shows accelerating melting in Antarctica, Mottram said.
Antarctica from 2017 to 2020 is still losing about 127 billion tons (115 billion metric tons) of ice a year, 23% less than at the beginning of the decade but overall 64% more than at the beginning of the decade. of the 1990s.
“While Greenland’s mass loss is outpacing that of Antarctica, there are problematic wild cards to the south, particularly the behavior of Thwaites Glacier,” nicknamed the Doomsday Glacier, said Mark Serreze, director of the center. Snow and Ice Agency, who was not part of the study.
The study authors used changes in gravity and the height of the ice and measured how much snow fell, how much snow melted, how much ice was lost as icebergs broke off and ate them up. below the warmer water that broke through the ice.
“This is important because sea level rise will displace and/or financially affect hundreds of millions of people, if not billions, and will probably cost trillions of dollars,” said Waleed Abdalati, an ice researcher at the University of Colorado. and former NASA chief scientist, who was not part of the study.
The study “is not so surprising as it is disturbing,” Abdalati said in an email. “A few decades ago, these vast ice deposits were assumed to be changing slowly, but by using satellite observations, field observations, and models.” techniques, we have come to learn that ice responds rapidly to our changing climate.”
(with information from AP)
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