Nearly half of the ice shelves (71 of the 162) surrounding Antarctica have shrunk over the past 25 years, releasing 7.5 trillion net tons of fresh meltwater into the oceans. It is the main conclusion of a study led by Benjamin Davison, from the University of Leeds (United Kingdom), published in the journal Science Advances.
This thinning occurred in almost all the ice shelves on the western side of Antarctica during the period analyzed, from 1997 to 2021. In contrast, most of the eastern ice shelves remained or increased in volume.
Ice shelves float in the seas surrounding Antarctica and are extensions of the ice sheet that covers much of the continent. They act as giant 'plugs' at the end of glaciers and slow the flow of ice into the oceans. When they thin, these 'plugs' weaken and the rate of ice loss from the glaciers increases.
Its disappearance represents a serious problem, because it produces important chain effects for the Antarctic ice system and global ocean circulation, which is a gigantic 'conveyor belt' that moves nutrients, heat and carbon from that sensitive polar ecosystem.
Researchers analyzed more than 100,000 satellite radar images to analyze the health of ice shelves in Antarctica. They were studied from 1997 to 2021. During those 25 years, scientists estimated that nearly 67 trillion tons of ice were exported to the ocean, which was offset by the addition of 59 trillion tons of ice to ice shelves, from so there was a net loss of 7.5 billion tons.
The thinning was most pronounced on almost all ice shelves on the western side of Antarctica. “There is a mixed picture of ice shelf deterioration and this has to do with ocean temperatures and ocean currents around Antarctica,” according to Davison.
This researcher emphasizes that "the western half is exposed to warm water, which can rapidly erode ice shelves from below, while much of East Antarctica is currently protected from nearby warm water by a strip of cold water on the coast." .
The author believes that human-induced global warming is likely to be a key factor in the ice loss, since if the melting were due to a natural variation in weather patterns there would have been some signs of ice regrowth on the western shelves. And it has not been like that.
Some of the largest ice losses were seen on the Getz Ice Shelf, where 1.9 trillion tons of ice were lost in 25 years. Only 5% of that figure was due to calving, when large chunks of ice break off the shelf and move toward the ocean. The rest was due to melting at the base of that ice shelf.
Similarly, 1.3 billion tons of ice were lost on the Pine Island Ice Shelf. About a third of that loss (450 billion tons) was due to landslides and the rest to melting at the bottom.
By contrast, the Amery Ice Shelf, on the other side of Antarctica, gained 1.2 trillion tons of ice. That ice barrier is surrounded by much colder waters.
