Scientists have reconstructed the past life of Antarctica's 'Doomsday Glacier', so nicknamed because its collapse could cause a catastrophic rise in sea levels.
They found that it began melting rapidly in the 1940s, according to a new study that offers an alarming insight into future melting, CNN reports.
Apocalypse Glacier PHOTO wikipedia NASA
The Thwaites Glacier in West Antarctica is the widest in the world and is about the size of Florida. Scientists knew it had been losing ice at an accelerated rate since the 1970s, but because satellite data only goes back a few decades, they didn't know exactly when significant melting began.
Now there is an answer to that question, according to a study published Monday in the journal Proceedings of the National Academy of Sciences.
Analyzing marine sediments extracted from the ocean floor, the researchers found that the glacier began to melt significantly in the 1940s, likely as a result of a very strong El Niño event – a natural climate fluctuation that tends to have a warming impact.
The glacier is melting fast PHOTO NASA
Since then, the glacier has failed to recover, which may reflect the increasing impact of human-caused global warming, according to the report.
It already contributes 4% to sea level rise
What happens to Thwaites will have global reverberations. The glacier already contributes 4% to sea level rise as it dumps billions of tonnes of ice into the ocean each year. Its complete collapse could raise sea levels by more than 1.5 meters.
But the glacier also plays a vital role in the stability of the West Antarctic Ice Sheet, acting as a cork that holds back the vast expanse of ice behind it. The collapse of Thwaites would undermine the stability of the ice sheet, which holds enough water to raise sea levels by at least 3 meters, causing catastrophic flooding globally.
The study's findings match previous research on neighboring Pine Island Glacier, one of Antarctica's largest ice streams, which scientists also found began melting rapidly in the 1940s.
What is happening to Thwaites is not specific to a single glacier
That makes the research significant, said Julia Wellner, an associate professor of geology at the University of Houston and one of the study's authors. What's happening to Thwaites is not specific to one glacier, but part of the larger context of a changing climate, she told CNN.
“If both glaciers are melting at the same time, that's further evidence that they are actually being forced by something.”Wellner said.
Ocean sediments were collected
To build a picture of Thwaites' life over the past nearly 12,000 years, researchers took an icebreaker vessel close to the edge of the glacier to collect ocean sediments from various depths.
They provide a historical timeline. Each layer provides information about the ocean and ice thousands of years ago. By scanning and dating the sediments, scientists were able to pinpoint when substantial melting began.
From this information, they believe that Thwaites' melt was triggered by the extreme El Niño phenomenon, which occurred at a time when the glacier was likely already in a melting phase, throwing it out of balance. “It's like being kicked when you're already sick, it will have a much greater impactWellner said.
The findings are alarming
The findings are alarming because they suggest that once big changes are started, it is very difficult to stop them, said James Smith, a marine geologist at the British Antarctic Survey and co-author of the study.
The glacier is located in West Antarctica PHOTO NASA
“Once an ice sheet retreat is set in motion, it can continue for decades, even if what triggered it doesn't get worse“, he told CNN.
While similar retreats have occurred much earlier in the past, the ice sheet has recovered and grown again, Smith said. But these glaciers “show no signs of recovery, which probably reflects the increasing influence of human-caused climate change.”
Ted Scambos, a glaciologist at the University of Colorado Boulder who was not involved in the research, said the study confirms and adds details to our understanding of how Thwaites' melt began.
A system that was already close to being unstable “took a heavy hit from a mostly natural event” Scambos said, referring to El Niño. “Other events that occurred more due to the climate warming trend took things further and started the widespread melting we see today“, he told CNN.
“Humans are changing the climate”
Martin Truffer, a physics professor at the University of Alaska Fairbanks, said the research shows that if a glacier is in a sensitive state, “a single event can throw him into a meltdown from which it is difficult to recover”.
“Humans are changing the climate, and this study shows that small continuous changes in climate can lead to step changes in glacier condition.” said Truffer, who was not involved in the research.
Antarctica is sometimes called the “sleeping giant” because scientists are still trying to understand how vulnerable this frozen and isolated continent may be as humans warm the atmosphere and oceans.
Wellner is a geologist — she focuses on the past, not the future — but she said this study provides important and alarming context for what could happen to the ice in this vital part of Antarctica.
It shows that even if a trigger for rapid melting has ended, that doesn't mean the response stops. “So if the ice is already retreating today,” she said, “just because we might stop warming, it might not stop melting”.
