Twenty-five years of satellite observations were used to rebuild a detailed history of Antarctica ice shelves.
Ice platforms are the floating protrusions of glaciers that flow through the land, and ring the entire continent.
European Space Agency data set confirms the melting process of shelves.
In all, they have dropped nearly 4,000 gigatons since 1994 – an amount of meltwater that could all but fill America’s Grand Canyon.
But the change here is not so much the fact that the shelves are losing mass – we already know that; relatively hot ocean water eats their bases. Instead, these are the finessed statements that can now be made about exactly where and when the waste occurred, and where the melting also takes place.
Some of this cold, fresh water enters the deep sea around Antarctica which undoubtedly influences the circulation of the ocean. And it could have implications for climate far from polar south.
“For example, there have been several studies that have shown that including the effect of Antarctic ice melt on models slows the rise in ocean temperatures, and this could actually lead to an increase in rainfall in the US,” explains by Susheel Adusumilli from the Scriptps Institute of Oceanography in San Diego.
Mr. Adusumilli and colleagues reviewed all observations made by Esa’s long series of radar altimeter missions – ERS-1, ERS-2, EnviSat and CryoSat-2.
Spacecrafts have been tracking changes in thickness on Antarctica ice shelves since the early 1990s.
Combining their data with ice speed information from other sources, and the outcomes of computer models – the Scripps team gained a high-resolution look at the melting pattern during the study.
As expected, there is already a lot of variation, with mass loss and gain, even within the same individual shelves. And the rate of mass loss over time has also increased. But the overall picture is clear: the shelves are a waste.
“We see that melting is always more than stable state values,” Mr. Adusumilli told BBC News. “You need a little melting to maintain the ice sheet balance. But what we found was an amount of melting ocean that was more than necessary to maintain this balance.”
The fascinating aspect of this study is that scientists can now also examine exactly where depth is going. Some of the floating ice platforms (the largest is the size of France) extend many hundreds of meters under the sea.
Researchers can tell from satellite data whether the waste occurs near thin sections of shelves or their borders, or deep in areas where glacier ice falls from the ground becomes pleasant and begins to float.
“This type of information can tell us a lot about the digestive processes involved, how they work – and the effects that water can dissolve,” says Scriptps’ Prof Helen Fricker.
“So, it’s not just the shelves that are melting. This is how they are melting – and where their melting water is injected into the ocean.”
Thin ice shelves do not directly contribute to rising sea levels. That is because the floating ice has moved its corresponding volume of water.
But there is an indirect result. If the shelves are weakened, the ice on the back can quickly flow into the ocean, and this will lead to sea level rise. This happens, and is measured by other satellites.
Prof David Vaughan is the director of science at the British Antarctic Survey. He is not connected to the study published in Nature Geoscience.
He told BBC News: “The Scripps team has created a map of Antarctica showing the thinness around the margin in a strip of red and blue colors. The detail on the coast is absolutely stunning.
“We can really identify the parts of the ice shelves that are most important in the thinning story. There will be a lot of oceanographers who spend a lot of time looking at where melting and thinning actually takes place, and trying to work. out exactly why those areas were affected. ”
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