The Antarctic ice shelves are melting rapidly, particularly in the west of the continent. Research based on satellite images shows that 40% of shelves are affected.
Researchers at the University of Leeds in the UK have conducted a health check on Antarctic ice shelves using satellite images taken over a 25-year period. And the results were bad. Indeed, the researchers found that 40% of the ice shelves surrounding Antarctica had lost volume between 1997 and 2021. Their findings were recently published in Science Advances.
The ice shelves in the west of the continent suffered the greatest loss of ice. On the eastern side, on the other hand, the volume of ice shelves remained unchanged or even increased. This difference is due to the temperature of the ocean and the ocean currents surrounding Antarctica: “The western half is exposed to warm water, which can rapidly erode the ice shelves from below, whereas much of East Antarctica is currently protected from nearby warm water by a band of cold water at the coast.”, explains, in a press release issued last week by the university, Dr. Benjamin Davison, a researcher at the University of Leeds who led the study,
To reach these conclusions, the researchers examined over 100,000 satellite radar images, mainly obtained by the CryoSat-2 and Sentinel-1 satellites. On this basis, they also calculated the loss of ice due to the reduction in volume. According to them, over the last 25 years, 67 billion tonnes of ice have ended up in the ocean. This loss was partially offset by the 59 billion tonnes of ice added to the shelves, ending in a 7.5 billion tonnes net loss.
Quite a surprise for the research team, who did not expect these results: “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.”
There are 162 ice shelves around Antarctica. These barriers are the extension of the huge ice cap that rests on the continent, and act as plugs, slowing the flow of ice from the glaciers. If ice shelves lose volume and become thinner, they can no longer play this retention role, increasing the volume of ice lost by glaciers.
The ice released by these barriers is freshwater. If this were to mix massively with seawater, it would not be without consequences. Indeed, salt water is denser and sinks to the depths of the ocean, acting as an engine for deep ocean circulation, a true conveyor belt that extends across the entire planet, transporting nutrients, carbon and heat. The less dense freshwater dilutes the saltwater, making it lighter and less likely to sink into the ocean, which can weaken the ocean circulation system. According to the authors of the article, more than 66 billion tonnes of freshwater were discharged into the Southern Ocean between 1997 and 2021.
A situation linked to global warming for researchers: “Many of the ice shelves have deteriorated a lot: 48 lost more than 30% of their initial mass over just 25 years.”, notes Anna Hogg, professor at the University of Leeds and co-author of the study. “This is further evidence that Antarctica is changing because the climate is warming. The study provides a baseline measure from which we can see further changes that may emerge as the climate gets warmer.”
The article also shows that satellites play a crucial role in monitoring Antarctica and its ice shelves. A surveillance that will be further strengthened in the coming years with the launch of other missions, such as CRISTAL, CIMR and ROSE-L.
Mirjana Binggeli, PolarJournal
More about this topic
