A NASA Modis satellite image of an Antarctic ice shelf taken on March 21, 2022 in this handout image obtained on March 25, 2022. NASA Modis satellite image/Handout via REUTERS
Sign up now for FREE unlimited access to Reuters.com
I am registering
LOS ANGELES, Aug 10 (Reuters) – Antarctica’s coastal glaciers are shedding icebergs faster than nature can restore the melting ice, doubling previous estimates of losses from the world’s largest ice sheet over the past 25 years, a satellite analysis showed in Wednesday.
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, raises new concerns about how quickly climate change is weakening Antarctica’s floating ice shelves and accelerating the rise of the world’s sea level.
The study’s key finding is that the net loss of Antarctic ice from coastal ice floes breaking off into the ocean is almost as great as the net amount of ice that scientists already knew was being lost through thinning caused by melting on the ice shelves below from warming seas.
Sign up now for FREE unlimited access to Reuters.com
I am registering
Combined, thinning and break-up have reduced the mass of the Antarctic ice shelves by 12 trillion tonnes since 1997, double the previous estimate, the analysis concluded.
The net loss of the continent’s ice sheet from calving alone over the past quarter-century covers nearly 37,000 square km (14,300 square miles), an area nearly the size of Switzerland, according to JPL scientist Chad Green, lead author of the study.
“Antarctica is falling apart at the edges,” Green said in a NASA news release about the findings. “And as the 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 huge. Antarctica holds 88% of the sea level potential of all the world’s ice, he said.
Ice shelves, permanent floating layers of frozen freshwater attached to land, take thousands of years to form and act as buttresses holding back glaciers that would otherwise easily slide into the ocean, causing seas to rise.
When ice shelves are stable, the long-term natural cycle of calving and regrowth keeps their size relatively constant.
In recent decades, however, warming oceans have weakened the shelves below, a phenomenon previously documented by satellite altimeters measuring the changing height of the ice and showing losses averaging 149 million tons a year from 2002 to 2020, according to NASA.
IMAGES FROM SPACE
For their analysis, Green’s team synthesized satellite imagery from visible, thermal-infrared and radar wavelengths to map ice flow and calving since 1997 more precisely than ever before over 30,000 miles (50,000 km) of the Antarctic coast .
Losses as measured by calving outpaced natural replenishment of the ice shelf by so much that researchers found Antarctica unlikely to return to pre-2000 glaciation levels by the end of this century.
Accelerated glacier breakup, like thinning ice, was most pronounced in West Antarctica, an area more affected by warming ocean currents. But even in East Antarctica, a region whose ice shelves were long thought to be less vulnerable, “we’re seeing more losses than gains,” Green said.
One calving event in East Antarctica that surprised the world was the collapse and breakup of the massive Conger-Glenzer Ice Shelf in March, possibly a sign of more weakening to come, Green said.
Eric Wolff, Royal Society Research Professor at the University of Cambridge, pointed to the study’s analysis of the behavior of the East Antarctic Ice Sheet during past warm periods and models for what might happen in the future.
“The good news is that if we stick to the 2 degrees of global warming that the Paris Agreement promises, sea-level rise due to the East Antarctic Ice Sheet should be moderate,” Wolf wrote in a commentary on the JPL study.
Failure to curb greenhouse gas emissions, however, risks contributing to “many meters of sea level rise over the next few centuries,” he said.
Sign up now for FREE unlimited access to Reuters.com
I am registering
Reporting by Steve Gorman in Los Angeles; Editing by Tom Hogue
Our standards: The Thomson Reuters Trust Principles.
Add Comment