A satellite analysis shows that Antarctica’s coastal glaciers are shedding ice faster than nature can replenish the crumbling ice, double previous estimates of damage from the world’s largest ice sheet. in the past 25 years.
The first study of its kind, led by researchers at From NASA The Jet Propulsion Laboratory (JPL) near Los Angeles and published in the journal Nature, raises new concerns about how rapidly climate change is weakening the South’s floating ice shelves. Polar and accelerating global sea levels.
The study’s key finding is that the amount of Antarctic ice lost from coastal glacial masses “born” into the ocean is nearly as much net ice as scientists know is lost due to thinning. by the melting of the ice shelves. from below by the warming sea.
Combined, thinning and childbirth have reduced the volume of Antarctic ice shelves by 12 trillion tons since 1997, twice as much as previously estimated, the analysis concluded.
According to JPL scientist Chad Greene, lead author of the study, the actual loss of continental ice over the past quarter-century spanned nearly 37,000 square kilometers (14,300 square miles), roughly the size of Switzerland.
“Antarctica is collapsing at its edges,” Greene said in a NASA announcement of the findings. “And as ice shelves shrink and weaken, the continent’s massive glaciers tend to accelerate and accelerate global sea-level rise.”
The consequences can be huge. Antarctica accounts for 88% of the sea level potential of all the world’s ice, he said.
Ice shelves, permanently frozen bodies of fresh water attached to land, take thousands of years to form and act like boots holding back glaciers that would otherwise slide easily into the ocean, causing sea level rise.
When the ice shelves are stable, the natural cycle of reproduction and growth over a long period keeps their size quite stable.
However, in recent decades, warming oceans have weakened the magnetic shelves from below, a phenomenon previously recorded by satellite altimeters that measure the changing heights of ice and give saw an average loss of 149 million tons per year from 2002 to 2020, according to NASA.
Images from space
For the analysis, Greene’s team synthesized satellite images from visible radar, thermal infrared and radar wavelengths to chart the flow and reproduction of glaciers since 1997 more accurately than ever before on Earth. 30,000 miles (50,000 km) of Antarctic coastline.
The measured losses from childbirth beyond the addition of natural ice shelves are so great that the researchers find that Antarctica is unlikely to return to pre-2000 glacier levels by the end of this century.
Accelerated glaciation, like ice thinning, is most pronounced in West Antarctica, an area more affected by warming ocean currents. But even in East Antarctica, an area where ice shelves have long been considered less vulnerable, “we’re seeing more losses than gains,” Greene said.
One calving event in East Antarctica that took the world by surprise was the collapse and disintegration of the Conger-Glenzer ice shelf in March, which could be a sign of greater weakening to come, Greene said. .
Eric Wolff, a Royal Society research professor at the University of Cambridge, points to the study’s analysis of how the East Antarctic ice sheet behaved during formerly warm periods and a model for what could be. happen in the future.
“The good news is that if we keep the 2 degrees of global warming promised by the Paris agreement, sea-level rise due to ice in East Antarctica will be modest,” Wolff wrote in a commentary on the JPL study. costly”.
However, if greenhouse gas emissions are not curbed, they risk contributing to “multi-meter sea level rise over the next few centuries”, he said.
© Thomson Reuters 2022
