Cadman Glacier on the western side of the Antarctic peninsula collapsed over a six-year timespan (2017-2023). It was pretty sudden in glaciological terms and caught researchers off guard. Warming ocean waters surrounding Antarctica in 2018 and 2019 are believed to trigger the dynamic change in the ice stream.
Cadman was 1.5 nautical miles at its mouth and seven miles long. It flowed northwest, emptying into Beascochea Bay south of Plas Point on the peninsula’s west side, the opposite side of the Larsen ice shelves (A, B, and C) on the east side, which collapsed over 2002 -2017.
Ridges and sea Mountains are believed to have prevented nearby glaciers (Funk and Lever) from sharing Cadman’s fate.
From Phys.org
By analyzing subsea oceanographic data, they believe a series of subsea rock structures called ridges or sills, at a depth of 200 meters and 230 meters, acts as a defensive barrier, deflecting channels of warmer water from reaching the glaciers. Although they warn that a rise in ocean warming could compromise the ability of the ridges to protect some glaciers.
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“What this new research shows is that apparently stable glaciers can switch very rapidly, becoming unstable almost without warning, and then thinning and retreating very strongly. This emphasizes the need for a comprehensive ocean observing network around Antarctica, especially in regions close to glaciers that are especially hard to make measurements.”
Writing in the paper, the researchers say what has happened to the Cadman Glacier can be seen as an example of a “glaciological tipping point,” where a system in a steady state can take one or two paths based on a change in an environmental parameter.
A tipping point was reached in 2018 caused by the arrival of unusually warm ocean water, which caused the ice shelf to unground. Reaching this tipping point caused the Cadman Glacier to increase its ice discharge by 28% in 13 months.
Meanwhile Iceberg A23a after thinning for thirty years from warming seas while wedged on a sea mountain in the Weddel Sea. Unlike Iceberg B22a protecting the ice tongue of Thaites, A23a did not protect the Filchner-Ronne ice shelf as it was grounded miles from the shelf where it had calved from in 1986.
