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Climate change: Satellites record the history of ice melting in Antarctica



Ice

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Ice shelves can extend hundreds of meters underwater

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25 years of satellite observations have been used to reconstruct the detailed history of the Antarctic ice shelves.

These ice sheets are the protrusion of glaciers that flow off the mainland and surround the entire continent.

The European Space Agency’s data set confirms the melting tendency of the shelves.

Overall, they have dropped by nearly 4,000 gigatons since 1994 – a quantity of melted water could fill the US Grand Canyon.

But the innovation here is not the fact that the shelves are dying – we already know that; The relatively warm seawater is eating their underside. Instead, it’s sophisticated claims that can now be made about exactly where and when the waste happened, as well as where the melted water went.

Part of this fresh, cold water has entered the deep sea around Antarctica, where it is certainly affecting ocean circulation. And this could have an impact on climate far beyond the south pole.

“For example, there have been a few studies showing that including the effect of Antarctic ice melting into models that slow global ocean temperature rise and that could actually lead to an increase precipitation in the US, “said Susheel Adusumilli from the Scripps Institute of Oceanography in San Diego.

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Artwork: Esa has been flying a series of radar satellites continuously since the early 1990s

Adusumilli and colleagues analyzed all observations made by Esa’s long series of radar altimeter missions – ERS-1, ERS-2, EnviSat and CryoSat-2.

These spacecraft have been monitoring changes in thickness in the Antarctic ice shelves since the early 1990s.

Combining their data with ice velocity information from other sources and the outputs of computer models – the Scripps team had a high-resolution view of the melt pattern during the study period.

As expected, there’s quite a bit of change, with mass drops and increases, even in the same single shelf. And the rate of mass loss over time also fluctuated. But the overall picture is clear: the shelves are wasted.

Mr Adusumilli told BBC News: “We have found that the melting is always above steady state value. “You need a quantity of melting just to keep the ice in balance. But what we’ve seen is a lot more melted by the ocean than is needed to keep it in balance.”

An intriguing aspect of this study is that scientists can now also track exactly where the melting took place at depth. Some of these floating ice sheets (the largest the size of France) stretch hundreds of meters below sea level.

From the satellite data, researchers can tell whether waste occurs near the thinnest parts of the racks or in front of them or deep below where the glacial glaciers come from land. become floating and start to float.

“That kind of information can tell us a lot about the melting processes involved, how they work – and the effects that melt water can have,” says Scripps professor Helen Fricker.

“So it’s not just the shelves that are melting. That’s how they melt – and where their melted water is pumped into the ocean.”

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Thin ice shelves do not directly contribute to sea level rise. That’s because the floating ice has taken the place of its equivalent volume of water.

But there is an indirect consequence. If the platforms are weakened, the ice behind the earth can flow more quickly into the ocean, and this will lead to sea level rise. This is happening and has been measured by other satellites.

Professor David Vaughan is the scientific director of the British Antarctic Survey. He was not involved in the research published in the journal Nature Geoscience.

He told BBC News: “The Scripps team created a map of Antarctica that shows the thinning around the edge into a mottled red and green band. The details of the coastline are absolutely extraordinary.

“Now we can really identify the parts of the ice shelf that are most important to the thinning story. There will be a lot of oceanographers spending a lot of time seeing where the process actually takes place. melt and thin, and try to work to find out exactly why those areas are affected. ”




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