A satellite analysis revealed on Wednesday that Antarctica’s coastline glaciers are shedding icebergs faster than nature can repair the collapsing ice, more than tripling previous estimates of losses from the world’s largest ice sheet during the past 25 years.

The groundbreaking study, spearheaded by experts at NASA’s Jet Propulsion Laboratory (JPL) near Los Angeles and published in the journal Nature, raises new concerns about how quickly climate change is weakening Antarctica’s floating ice shelves and hastening global sea-level rise.

The study’s primary discovery was that the net loss of Antarctic ice from coastal glacier pieces “calving” off into the ocean is roughly equal to the net quantity of ice scientists already knew was being lost due to thinning caused by warming seas melting ice shelves from below.

The investigation revealed that thinning and calving have reduced the bulk of Antarctica’s ice shelves by 12 trillion tons since 1997, more than double the previous estimate.

According to JPL scientist Chad Greene, the study’s principal author, the net loss of the continent’s ice sheet through calving alone during the last quarter-century spans nearly 37,000 sq km (14,300 sq miles), an area nearly the size of Switzerland.

“Antarctica is crumbling at its edges,” Greene stated in a NASA press release announcing the findings. “And when ice shelves dwindle and weaken, the continent’s massive glaciers tend to speed up and increase the rate of global sea level rise.”

The ramifications might be massive. According to him, Antarctica has 88% of the world’s ice potential for sea level rise.

Ice shelves, which are permanent floating sheets of frozen freshwater tied to land, build over thousands of years and act as buttresses, holding back glaciers that would otherwise flow off into the ocean, causing sea levels to rise.

When ice shelves are stable, the natural cycle of calving and re-growth keeps their size relatively constant over time.

Warming waters, on the other hand, have damaged the shelves from below, a phenomenon previously recorded by satellite altimeters measuring the changing height of the ice and revealing losses average 149 million tons per year from 2002 to 2020, according to NASA.

Greene’s team used satellite photos from visible, thermal-infrared, and radar wavelengths to map glacial flow and calving since 1997 more precisely than ever before along 30,000 miles (50,000 km) of Antarctic coastline.

Calving losses outperformed natural ice shelf renewal so much that researchers believe Antarctica may be unable to return to pre-2000 glacier levels by the end of the century.

The rapid glacier calving, like ice thinning, was particularly noticeable in West Antarctica, which has been struck hardest by rising ocean currents. Even in East Antarctica, where ice shelves were previously thought to be less fragile, “we’re seeing more losses than gains,” Greene said.

The collapse and breakup of the enormous Conger-Glenzer ice shelf in March surprised the world, according to Greene, and could be a warning of further weakness to come.

The study’s investigation of how the East Antarctic ice sheet behaved during warm periods in the past and projections for what might happen in the future, according to Eric Wolff, a Royal Society research professor at the University of Cambridge.

“The good news is that if we keep to the 2 degrees of global warming that the Paris agreement promises, the sea level rise due to the East Antarctic ice sheet should be modest,” Wolff wrote in a commentary on the JPL paper.

Failure to reduce greenhouse gas emissions, on the other hand, risks contributing to “many meters of sea level rise over the next few centuries,” he said.

Source: Reuters


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