For the first time, researchers were able to access data under the Thwaites Glacier, also known as the “Doomsday Glacier”. They find that the glacier’s supply of warm water is greater than previously thought, raising concerns about a faster meter
UNIVERSITY OF GOTHENBURG
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PICTURE: PHOTO DES UNCREWED SUBMARINE RAN show more CREDIT: FILIP STEDT
For the first time, researchers were able to access data under the Thwaites Glacier, also known as the “Doomsday Glacier”. They find that the glacier’s supply of warm water is greater than previously thought, raising concerns about faster melting and accelerating ice flow.
With the help of the unscrewed Ran submarine, which found its way under the Thwaites glacier front, the researchers have made a number of new discoveries. Professor Karen Heywood from the University of East Anglia commented:
“This was Ran’s first venture into polar regions, and their exploration of the waters beneath the ice shelf has been far more successful than we could have hoped. We plan to build on these exciting discoveries with additional missions under the ice over the next year. “
The dive boat measured, among other things, the strength, temperature, salinity and oxygen content of the ocean currents flowing under the glacier.
Global sea level is affected by how much ice is on land, and the greatest uncertainty in forecasts is the future evolution of the West Antarctic ice sheet, says Anna Wåhlin, professor of oceanography at Gothenburg University and lead author of the new study now in Science Advances published.
Impact on global sea level
The ice sheet in West Antarctica accounts for about ten percent of the current sea level rise. But the ice in West Antarctica also has the greatest potential for increasing this rate, as the world’s fastest changes take place in the Thwaites Glacier. Due to its location and shape, Thwaites is particularly sensitive to warm and salty ocean currents that find their way underneath.
This process can lead to accelerated melting at the bottom of the glacier and movement inland in what is known as the grounding zone, the area where the ice changes from resting on the seabed to swimming in the ocean.
Due to its inaccessible location, far from research stations, in an area normally blocked by thick sea ice and many icebergs, there has been a great lack of in-situ measurements in this area. This means that there are large gaps in knowledge of the ice-ocean boundary processes in this region.
First measurements carried out
In the study, the researchers present the results of the submersible, which measured the strength, temperature, salinity and oxygen content of the ocean currents flowing under the glacier.
“These were the first measurements ever taken under the Thwaites Glacier,” says Anna Wåhlin.
The results were used to map the ocean currents beneath the floating part of the glacier. The researchers discovered that there is a deep link to the east through which deep water flows from Pine Island Bay, a link previously believed to be blocked by an underwater ridge.
The research group also measured heat transport in one of the three channels that carry warm water from the north to the Thwaites Glacier. “The channels through which warm water can access and attack thwaites were not known to us before the investigation. With the help of sonars on the ship, which are nested with a very high-resolution ocean map from Ran, we were able to determine that there are different paths that water leads into and out of the cavity of the ice shelf, influenced by the geometry of the seabed “, says Dr. Alastair Graham, University of South Florida.
The measured value of 0.8 TW corresponds to a net melt of 75 km3 of ice per year, which is almost as large as the total bottom melt in the entire ice shelf. Although the amount of ice that melts as a result of the hot water is not much compared to other global freshwater sources, heat transport has a large impact locally and can indicate that the glacier is not stable over time.
Not sustainable over time
The researchers also found that large amounts of meltwater flowed north from the front of the glacier.
Variations in salinity, temperature, and oxygen levels indicate that the area under the glacier is a previously unknown active area where different bodies of water meet and mix, which is important for understanding the melting processes at the ice base.
The observations show that warm water is approaching fixed points from all sides, at critical points where the ice is connected to the sea floor and gives the ice shelf stability. Melting around these fixed points can lead to instability and retreat of the ice shelf and then the upstream glacier flowing from land. Dr. Rob Larter of the British Antarctic Survey commented:
“This work shows how and where warm water affects the Thwaites Glacier, is influenced by the shape of the seabed and the base of the ice shelf, as well as the properties of the water itself. The successful integration of new seabed survey data and observations of water properties from the Ran missions shows the benefits of the multidisciplinary ethos within the International Thwaites Glacier Collaboration. “
“The good news is that, for the first time, we are collecting the data needed to model the dynamics of the Thwaite Glacier. These data will help us to better calculate how the ice will melt in the future. With the help of new technologies, we can improve the models and reduce the great uncertainty that now prevails with global sea level fluctuations. “Says Anna Wåhlin.
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From EurekAlert!
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