Scientists may have identified the Achilles’ heel as Thwaites Glacier.
This Antarctic giant is melting at a rapid rate, throwing billions of tons of ice into the ocean every year and raising global sea levels.
Now, a British-American team has surveyed deep sea floor canals in front of the glacier that almost certainly provide an outlet for warm water to infiltrate and attack the bottom of Thwaites.
It is information that will be used to try to predict the future of the ice stream.
“These channels have never been previously mapped with this kind of detail,” said Dr. Kelly, “and what we discovered is that they are in fact much larger than anyone would have thought – up to 600 meters deep. Think of six consecutive soccer fields.” Hogan from the British Antarctic Survey (BAS).
She told BBC News: “And because it is so deep and so wide – this allows a lot of water to reach the floating façade of the Twits and its melting, as well as the ice that falls on the sea floor.”
Why is Thwaites Glacier so important?
Thwaites flow from West Antarctica, and are roughly the size of Great Britain.
It is a majestic sight, with its blossoming façade, or “ice shelf,” as it rushes away into the sea and sets off huge icebergs. But satellite observations indicate that this glacier is melting at an accelerating rate.
In the 1990s, it was losing just over 10 billion tons of ice annually. Today, it is more than 80 billion tons. The melting is thought to be due to an influx of relatively warm bottom water being drawn from the wider ocean.
Currently, Thwaites’ ice loss contributes about 4% to the annual rise in global sea levels, with the potential to add 65 cm in total if the entire glacier collapses.
Nobody believes this will happen in the short to medium term, but Thwaites is particularly vulnerable in a warming world, and scientists would like to know precisely how quickly any changes will occur.
What does the latest search show?
The UK and the US teamed up in 2019 to investigate Thwaites.
Their scientists sailed a ship equipped with an echo-probe that reached the icy slopes of the glacier, to trace the shape of the sea floor below.
A plane was also moved back and forth across the rack to measure small differences in the force of gravity. These deflections reflect the ripples of the sea floor below the shelf.
Combined, the two datasets now provide the best view yet of the Tawites’ main terrain. They trace the path of a network of deep channels that cut through a ridge before they coalesce to form a main cavity under the ice shelf.
“The connected channels that we detailed in detail for the first time are the potential pathways for warm waters to enter the depths of the ocean and cause damage at that point where the iceberg remains anchored to the sea floor, as it begins to rise and float,” explained BAS Fellow Dr. Tom Jordan, “but also to melt The base of the ice shelf, which if weakened, would make the ice flow faster upstream into the glacier. ”
How will the new survey information be used?
Scientists need data from the real world to assemble their models so that they get realistic results when they run to simulate possible future behavior.
The new information is improving the volumes of warm water introduction that may be considered possible under a variety of scenarios.
When conducting the survey, scientists now have a better idea of the general roughness of the sea floor.
This tells them about the types of velocities that returning ice to glaciers can achieve as it slides through rocks and sediments. What the researchers produced, if you wanted to, was a kind of “stickiness indicator” to further restrict computer models.
What is likely to happen in the near future?
Currently, the eastern side of the ice shelf is attached to a large ledge, which gives it stability. Dr Robert Larter of Bass says the current melting trend indicates that this situation will not last longer.
He told BBC News: “When the eastern ice shelf separates, the ice will spread, become thin, and eventually disintegrate, as we see happening now on the (central) glacier tongue.” “Even before an ice shelf disintegrates, loosening and rotating the ice shelf will reduce the supporting effect of the ice shelf on the upstream glacier, increasing the velocity of ice flow. This, in turn, will increase the speed of the glacier’s thinning and retreat of the grounding line.”
British and American scientists had to temporarily suspend their investigations into Thwaites due to the Covid-19 crisis.
Teams were due to return to the glacier this Australian summer, but the remoteness of the location means the stakes are too high if anyone gets sick. Once the coronavirus outbreak is properly contained, scientists will return.
“It’s amazing that you go to a place like Thwaites to see the changes taking place right in front of your eyes,” said Dr. Hogan. “When we were there in 2019, we had direct access to the slopes of the ice shelf, and the reason we were able to do that and make our observations is that the icebergs and sea ice that had always been there throughout history started to disappear.”