Satellite images show that the Antarctic ice shelf is collapsing faster than previously thought

A satellite analysis showed, Wednesday, that coastal glaciers in Antarctica are removing icebergs at a faster rate than nature’s ability to replenish broken ice, doubling previous estimates of losses from the world’s largest ice sheet over the past 25 years.

The first-of-its-kind study, led by researchers at NASA’s Jet Propulsion Laboratory (JPL) near Los Angeles and published in the journal Nature, has raised new concerns about how quickly climate change is weakening Antarctica’s floating ice shelves and accelerating their ascent. global sea levels.

The study’s main finding was that the net loss of Antarctic ice from “breeding” coastal glaciers pieces to the ocean is roughly the size of the net amount of ice that scientists already knew was lost due to ice thinning caused by melting ice shelves. from below by rising sea temperatures.

The analysis concluded that thinning and calving together have reduced the mass of Antarctica’s ice shelves by 12 trillion tons since 1997, twice the previous estimate.

According to JPL scientist Chad Green, lead author of the study, the net loss of ice cover on the continent from birth alone in the past quarter century spans nearly 37,000 square kilometers (14,300 sq mi), an area roughly the size of Switzerland.

“Antarctica is collapsing at its edges,” Green said in NASA’s announcement of the results. “And as the ice shelves dwindle and weaken, the massive glaciers on the continent tend to accelerate and increase the rate of global sea level rise.”

The consequences could be dire. He said Antarctica has 88% of the sea-level potential of all the world’s ice.

Ice shelves, permanent floating sheets of frozen fresh water attached to the land, take thousands of years to form and act like struts preventing glaciers that would have easily slipped into the ocean, causing the seas to rise.

When ice shelves are stable, the natural, long-term cycle of birth and regrowth keeps their size fairly constant.

But in recent decades, warming oceans have weakened the shelves from below, a phenomenon previously documented by satellite altimeters that measure the changing height of ice and showing losses averaging 149 million tons per year from 2002 to 2020, according to NASA.

image from space

For their analysis, Greene’s team compiled satellite images from visible, infrared, thermal, and radar wavelengths to chart the glacial flow and calving since 1997 more accurately than ever before over 30,000 miles (50,000 km) from the Antarctic coast.

Measured losses from calving calves have exceeded natural ice shelf regeneration so much that researchers have found that Antarctica is unlikely to return to pre-2000 levels of glaciers by the end of this century.

The acceleration of ice birth, such as ice thinning, was most pronounced in West Antarctica, an area hit hardest by warming ocean currents. Even in East Antarctica, a region whose ice shelves have long been considered less vulnerable, Green said, “we’re seeing more losses than gains.”

One of the East Antarctic birth events that surprised the world, Green said, was the collapse and disintegration of the massive Konger-Glenzer ice shelf in March, perhaps a sign of greater weakness to come.

Eric Wolf, Royal Society Research Professor at the University of Cambridge, points to the study’s analysis of how the East Antarctic ice sheet behaved during warm periods in the past and models for what might happen in the future.

“The good news is that if we stick to the two degrees of global warming promised by the Paris Agreement, sea level rise due to the East Antarctic ice sheet should be modest,” Wolf wrote in a commentary on the JPL study.

He said failure to reduce greenhouse gas emissions would risk contributing “several meters of sea level rise over the next few centuries”.

(Covering by Steve Gorman in Los Angeles). Edited by Tom Hogg

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