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Measurements from an underwater spacecraft that entered the so-called Doomsday Glacier in western Antarctica, show that the inflow of hot water to the glacier is greater than scientists have hitherto thought. If the giant glacier melts, the sea level will be affected.

With the help of the unmanned submarine Ran, which entered under Thwaite’s glacier front, the researchers have obtained data on the strength, temperature, salinity and oxygen content of the ocean currents that enter under the glacier. Thwaites Glacier is called the Doomsday Glacier because it binds such large amounts of ice that a meltdown would have severe consequences.

  • The global water level is affected by how much ice is on land, and the biggest uncertainty in the forecasts is the future development of the ice sheet in West Antarctica, says Anna Wåhlin, professor of oceanography at the University of Gothenburg, one of the researchers behind the study.
  • This was Ran’s first effort in the polar region and the investigation of the water under the ice shelf was more successful than we dared to hope for. We plan to follow up on these exciting results with additional research assignments under the ice next year, says Professor Karen Heywood from the University of East Anglia, and an honorary doctor at the University of Gothenburg’s Faculty of Science.
Thwaites Glacier occupies an area as large as half of Sweden, and is due to its location in a deep basin sensitive to changes in the sea. Image: NASA

Affects the water level

The ice sheet in West Antarctica currently accounts for about ten percent of the total water level rise. And the fastest changes in the melting of glaciers are taking place in the Thwaites Glacier. As the continent slopes inwards below the glacier, it is sensitive to warm and salty ocean currents finding their way under it.

  • This process can lead to an accelerated melting taking place at the bottom of the glacier and that the so-called baseline, the area where the ice transitions from resting on the seabed to flowing, pulls inwards towards the center of the continent, says Anna Wåhlin.

Due to its inaccessible location, far from research stations, in an area that is usually blocked by thick sea ice and many icebergs, there has been a great shortage of sightings from this area. This means that so far there has been a lack of knowledge about the melting processes.

First measurements performed

The results of the measurements on Ran have been used to map the underwater currents under the floating part of the glacier. Researchers have discovered that deep water is connected to the east bay of Pine Island Bay, a road that was previously thought to be blocked by an underwater ridge.

The research group has also measured the heat transport in one of the three canals that lead hot water into the Thwaites Glacier from the north. The value measured there, 0.8 TW, corresponds to a net melting of 75 km3 of ice per year, which is almost as much as the total melting in the entire glacier.

Although the amount of ice that melts as a result of the hot water is not much seen globally, the heat transport has a large effect locally and may indicate that the glacier is not stable over time.

Not sustainable over time

The researchers also noted that large amounts of meltwater flowed north from the front of the glacier.

  • Variations in salinity, temperature and oxygen content indicate that the area under the glacier is a previously unknown active area where several different bodies of water of different densities meet and mix with each other, which is important for understanding the melting processes at the bottom of the ice, says Anna Wåhlin.

The observations show that points where the ice is currently connected to the seabed, which gives stability to the glacier on land, are affected by warm sea currents from several directions, which indicates that these points are not sustainable over time.

  • But the good news is that we are now, for the first time, collecting data that is necessary to model the dynamics of Thwaite’s glacier. These data will help us better calculate ice melting in the future. With the help of new technology, we can improve the calculation models and reduce the great uncertainty that now prevails around global water level variations, says Anna Wåhlin.

This article was published originally by forskning.se

Article source: forskning.se

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