Shortly after the millennium, in March 2002, iceberg B-22A broke off the top of Thwaites Glacier in West Antarctica: the largest in the Amundsen Sea, originally 85 kilometers long and up to 64 kilometers wide. The giant didn’t get very far afterwards, because it got stuck on the ground around 100 kilometers in front of the tongue of ice, also known as “Doomsday Glacier”, and thus acted like a stabilizing barrier on the sea ice and shelf ice behind it. But that has obviously changed in recent months, as shown by satellite images presented by Simon Gascoin of the French CNRS in early January 2023.
This could now have consequences for the entire region: B-22A protected the thinner sea ice lying between itself and the ice shelf, which forms here every winter. And this in turn helped stabilize the ice shelf which ultimately slows down Thwaites Glacier and thus preserves its condition. Without the iceberg, the sea ice is likely to become more unstable due to increased exposure to storms and the sea. In a kind of chain reaction, the front of the ice shelf also threatens to become more brittle. Should it eventually disintegrate, Thwaites Glacier should flow faster into the Antarctic Ocean, contributing to more sea level rise.
The ice shelf in front of the ice tongue has shrunk significantly in recent years. Currently, a ridge of mountains lying beneath the sea ensures that what is left is held off the mainland. However, recent studies show that the ice is melting from below because relatively warm seawater is penetrating fissures at the base of the ice shelf, reducing its stability. Many glaciologists therefore assume that the ice shelf could disintegrate in the next few years.
Since Thwaites Glacier itself is in a basin on land, seawater could then infiltrate beneath it and also melt from the base. In addition, its flow speed should then also increase and it should flow faster into the open sea. Many experts then assume a self-reinforcing mechanism that could ultimately lead to a large-scale collapse of the glacier. Since this holds back the West Antarctic ice sheet like a cork in a bottle, this would then also start to move.
The collapse of Thwaites would raise sea levels by 65 centimeters, and that of the West Antarctic Ice Sheet by more than 3 meters. It is of little consolation that this process is likely to drag on for several centuries.
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The original of this article “Thwaites Glacier causes concern – decay would have serious consequences” comes from Spektrum.de.
