Wednesday, July 24, 2024

Antarctica’s ice shelves reduced over 40 per cent in 25 yrs: Study

A whopping 71 of the 162 ice shelves or more than 40 per cent that surround Antarctica have reduced in volume over 25 years from 1997 to 2021, according to a new study.

The study, published in the journal ‘Science Advances’, found that over the 25 years, almost 67 trillion metric tonnes of ice was exported to the ocean, which was offset by 59 trillion metric tons of ice being added to the ice shelves, giving a net loss of 7.5 trillion metric tonnes.

The team from University of Leeds in the UK found that almost all the ice shelves on the western side of Antarctica experienced ice loss. In contrast, most of the ice shelves on the eastern side stayed the same or increased in volume.

“There is a mixed picture of ice-shelf deterioration, and this is to do with the ocean temperature and ocean currents around Antarctica,” said Dr. Benjamin Davison, a research fellow at the varsity, who led the study.

“We expected most ice shelves to go through cycles of rapid, but short-lived shrinking, then to regrow slowly. Instead, we see that almost half of them are shrinking with no sign of recovery,” he added.

He believes human-induced global warming is likely to be a key factor in the loss of the ice. If it was due to natural variation in climate patterns, there would have been some signs of ice re-growth on the western ice shelves.

The researchers analysed over 100,000 satellite radar images to produce this major assessment of the “state of the health” of the ice shelves.

Some of the biggest ice losses were observed on the Getz Ice Shelf, where 1.9 trillion metric tonnes of ice was lost over the 25-year study period. Just 5 per cent of that was due to calving, where large chunks of ice break away from the shelf and move into the ocean. The rest was due to melting at the base of the ice shelf.

Similarly on the Pine Island Ice Shelf, 1.3 trillion metric tonnes of ice was lost. Around a third of that loss — 450 billion metric tonnes — was due to calving. The rest was due to melting from the underside of the ice shelf.

In contrast, the Amery Ice Shelf — on the other side of Antarctica — gained 1.2 trillion metric tonnes of ice. It is surrounded by much colder waters.

“The study has generated important findings. We tend to think of ice shelves as going through cyclical advances and retreats. Instead, we are seeing a steady attrition due to melting and calving,” said co-author Professor Anna Hogg, also from Leeds.

“Many of the ice shelves have deteriorated a lot: 48 lost more than 30 per cent of their initial mass over just 25 years. This is further evidence that Antarctica is changing because the climate is warming,” she said.

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