2023-11-28 18:31:49
MADRID, 28 Nov. (EUROPA PRESS) –
Antarctica’s seemingly stable glaciers can “change very quickly” and lose large amounts of ice as a consequence of ocean warming.
The discovery, published in the magazine ‘Nature Communications’came after a research team led by Benjamin Wallis, a glaciologist at the University of Leeds, used satellites to track the Cadman Glacier, that empties into the bay of Beascocheaon the western Antarctic Peninsula.
Between November 2018 and May 2021, the glacier went back eight kilometers as the ice shelf at the end of the glacier – where the ice extends out to sea and anchors to the seafloor in what is known as the stranding zone – collapsed.
The ice shelf would have acted as a buttress, slowing the movement of the glacier towards the sea. Surrounded by warmer ocean waters, scientists believe the ice shelf thinned and broke away from the ground, so it could no longer contain the glacier.
As a result, the speed at which the glacier was flowing rapidly accelerated – doubling its speed – and the amount of ice it dumped into the sea in the form of icebergs increased, through a process known as iceberg calving.
“We were surprised to see the speed at which Cadman went from a seemingly stable glacier to one where we observed sudden deterioration and significant ice loss –recalls Wallis it’s a statement–. What was also curious was that the neighboring glaciers in this part of the Western Antarctic Peninsula did not react in the same way, which may hold important lessons for how we can better project how climate change will continue to affect this important and sensitive polar region”.
“Our study brought together data from three decades, nine different satellite missions and in situ oceanographic measurements to understand the changes taking place in Antarctica,” he continues. “This shows how important it is to have long-term monitoring of the polar regions of the Earth with a series of sensors that each tell us a different part of the story.
According to scientists, the Cadman Glacier is now in a state of “substantial dynamic disequilibrium.” The glacier ice has continued to thin, losing height at a rate of about 20 meters per year. This is equivalent to the height loss of a five-story building each year.
In addition, about 2.16 billion tons of ice from the Cadman Glacier are dumped into the ocean each year.
Unusually high ocean water temperatures in early 2018/19 around the Western Antarctic Peninsula are believed to have triggered the rapid dynamic change in the Cadman Glacier system.
By analyzing historical satellite data, scientists believe that warmer ocean waters gradually thinned the glacier’s ice shelf since the early 2000s. and possibly since the 1970s.
The warmer water did not move along the surface of the ocean, but rather through the depths of the water column.. This warmer water may have reached the ice shelf, where it is stranded on the sea floor. The result is that the ice shelf begins to melt from the bottom up.
In 2018/19, the ice shelf was so thin that it broke free of the stranding zone and began to float, in effect slipping the anchor and allowing the Cadman Glacier to drain more ice into the seas, but the science team was still faced with to the big question of why the Cadman Glacier had collapsed when the neighboring Funk and Lever glaciers remained relatively stable.
By analyzing underwater oceanographic data, they believe that a series of underwater rock structures called ridges or sills, at a depth of 200 meters and 230 meters, act as a defensive barrier, diverting channels of warmer water so that they do not reach the glaciers. . However, they warn that increased ocean warming could endanger the ability of ridges to protect some glaciers.
Professor Michael Meredith, from the British Antarctic Survey and one of the authors of the study, points out that it has long been known that the ocean around Antarctica is warming rapidly, and that this poses a significant threat to glaciers and the ice sheet. , with consequences for global sea level rise.
“This new research shows that apparently stable glaciers can change very quickly, becoming unstable almost without warning, and then thinning and retreating very strongly,” he underlines. around Antarctica, especially in regions close to glaciers that are especially difficult to measure.”
In the study, the researchers say that what happened to the Cadman Glacier can be considered an example of a “glaciological tipping point,” in which a steady-state system can take one or two paths depending on a change in an environmental parameter.
In 2018, a tipping point was reached, caused by the arrival of unusually warm ocean water, which caused the ice shelf to break away. Reaching this tipping point caused the Cadman Glacier to will increase your ice discharge by 28% in 13 months.
Researchers say other glaciers on the Antarctic Peninsula may be vulnerable to similar sudden changes due to underwater geology.
#Rapid #retreat #Antarctic #glacier #due #warmer #sea