Scientists may have just identified the Achilles heel of the Thwaites Glacier.

This Antarctic colossus is rapidly melting, dumping billions of tons of ice into the ocean each year and raising global sea levels.

Now the British-American team has explored the deep seabed channels in front of the glacier, which almost certainly provide warm water access to penetrate and attack the lower Thwaite.

This information will be used to try to predict the future of the ice stream.

“These channels have never been mapped in this detail before, and we found that they are actually much larger than anyone thought – up to 600 meters deep. Think of six football pitches in a row, ”said Dr. Kelly. Hogan of the British Antarctic Survey (BAS).

“And because they are so deep and so wide, it allows much more water to enter and melt Thwaites’ floating front and its ice on the seabed,” she told BBC News.

Why is Thwaites Glacier so important?

Located west of the Antarctic continent, Thwaites is almost as large as Great Britain.

It is a majestic sight with its moving front, or “ice shelf”, stretching far out to sea and discarding huge icebergs. But satellite monitoring shows that this glacier is melting faster and faster.

In the 1990s, it lost just over 10 billion tons of ice per year. Today it is more than 80 billion tons. The melting is believed to be due to the influx of relatively warm bottom water from the wider ocean.

Currently, ice loss at Thwaites represents approximately 4% of the annual rise in sea level, with the potential for a total of 65 cm to increase if the entire glacier collapses.

No one thinks this will happen in the short to medium term, but Thwaites is considered particularly vulnerable to warming, and scientists would like to know how quickly any change could occur.

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What does the latest research show?

In 2019, the UK and the US joined forces to investigate the Thwaites case.

Their scientists sent a ship equipped with an echo sounder straight to the icy cliffs of the glacier to trace the shape of the seabed below.

The aircraft also flew back and forth across the shelf to measure small changes in gravity. These deviations reflected the unevenness of the seabed under the shelf.

The two datasets taken together now provide the best view of Thwaites topography. They trace the path of a network of deep channels that cross the ridge and then join to form a large cavity beneath the ice shelf.

“The associated channels, which we first mapped in detail, are potential pathways for deep-sea warm water to penetrate and damage it at the point where the glacier still rests on the seabed where it starts to rise. and swim, “BAS colleague Dr. Tom Jordan explained,” but also melt the base of the ice shelf, which, if you loosen up, will cause the ice to flow further upstream at a faster rate. ”

How will the new survey information be used?

Scientists need real-world data to capture their models so that they can get realistic results when modeling possible future behavior.

The new information clarifies the amount of warm water infiltration that can be considered possible under various scenarios.

Through their research, scientists now have a better understanding of the overall roughness of the seabed.

This tells them how fast ice can reach deep in the glacier as it slides over rocks and sediments. What the researchers have developed, if you like, is a kind of “stickiness index” that further limits computer models.

What could happen in the near future?

At the moment, the eastern side of the ice shelf is entangled with a large ridge, which gives it stability. But the current melting trend suggests that this situation won’t last long, says Dr. Robert Larter of BAS.

“When the East Ice Shelf comes loose, the ice will expand and thin out, eventually collapsing as we see what’s happening in the (central) tongue of the glacier,” he told BBC News. “Even before the ice shelf breaks down, detachment and thinning will reduce the supporting effect of the ice shelf on the glacier upstream, resulting in an increase in ice flow rate. This, in turn, will further accelerate the thinning of the glacier and the retreat of the ground line. … “

British and American scientists were forced to temporarily suspend their research at Thwaites due to the Covid-19 crisis.

The teams were supposed to return to the glacier this southern summer, but the remoteness of the site means too much risk in case someone falls ill. However, once the coronavirus outbreak is properly contained, scientists will return.

“It’s amazing to be in a place like Thwaites and see the changes happening right before your eyes,” said Dr. Hogan. “When we were there in 2019, we were able to get right up to the rocks of the ice shelf, and the reason we were able to do this and make our observations was because the icebergs and sea ice that have always been here historically are starting to disappear. … “

The latest study is published in two articles in The Cryosphere and can be accessed. Here and Here…

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