Los Angeles’ Antarctic coastal glaciers are releasing icebergs faster than nature can replenish crumbling ice, doubling previous estimates of losses from the world’s largest ice sheet over the past 25 years, a satellite analysis showed Wednesday. fair (10).
The first study of its kind, led by researchers at NASA’s Jet Propulsion Laboratory (JPL) near Los Angeles and published in the journal Nature, raises new concern about how quickly climate change is weakening Earth’s floating ice shelves. Antarctica and accelerating the rise of global sea levels.
The study’s main finding was that the net loss of Antarctic ice from pieces of coastal glaciers “breaking up” into the ocean is almost as large as the net amount of ice that scientists already knew was being lost due to thinning caused by melting shelves. of ice from below by the warming of the seas.
Together, thinning and loosening have reduced the mass of Antarctica’s ice shelves by 12 trillion tonnes since 1997, double the previous estimate, the analysis concluded.
The net loss of the continent’s ice sheet through shedding alone over the past quarter-century covers nearly 37,000 square kilometers, an area nearly the size of Switzerland, according to JPL scientist Chad Greene, the study’s lead author.
“Antarctica is crumbling at its edges,” Greene said in a NASA announcement about the findings. “And when ice shelves shrink and weaken, the continent’s massive glaciers tend to accelerate and increase the rate of global sea level rise.”
The consequences can be enormous. Antarctica holds 88% of the sea-level potential of all the world’s ice, he said.
Ice shelves, permanent floating sheets of frozen freshwater tethered to land, take thousands of years to form and act as foothills holding glaciers that would otherwise slide easily into the ocean, causing the seas to rise.
When ice shelves are stable, the natural long-term cycle of calving and regrowth keeps their size fairly constant.
In recent decades, however, warming oceans have weakened the shelves beneath, a phenomenon previously documented by satellite altimeters that measure the change in ice height and show losses averaging 149 million tonnes a year from 2002 to 2020, according to to NASA.
satellite images
For their analysis, Greene’s team synthesized satellite imagery of visible wavelengths, thermal infrared, and radar to map glacial flow and calving since 1997 more accurately than ever before over 50,000 kilometers off the coast of Antarctica.
Measured calving losses outpaced the natural replenishment of ice shelves so much that researchers thought it unlikely that Antarctica could return to pre-2000 glacier levels by the end of this century.
Accelerated glacial detachment, like the thinning of the ice, was most pronounced in West Antarctica, an area hardest hit by warming ocean currents. But even in East Antarctica, a region whose ice shelves were considered less vulnerable, “we’re seeing more losses than gains,” Greene said.
One East Antarctic birth event that took the world by surprise was the collapse and disintegration of the massive Conger-Glenzer ice shelf in March, possibly a sign of further weakening to come, Greene said.
Eric Wolff, a research professor at the Royal Society at the University of Cambridge, pointed to the study’s analysis of how the East Antarctic ice sheet behaved during past warm periods and models for what might happen in the future.
“The good news is that if we maintain the 2ºC of global warming that the Paris agreement promises, sea level rise due to the East Antarctic Ice Sheet should be modest,” Wolff wrote in a commentary on the JPL study. .
Failure to curb greenhouse gas emissions, however, would risk contributing “many meters of sea level rise in the coming centuries,” he said.
Source: CNN Brasil
