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Sea ice around Antarctica hits record low

Sea ice around Antarctica has hit a record low in four decades of observations, a new analysis of satellite images shows.

As of Tuesday, ice covered 750,000 square miles around the Antarctic coast, below the previous record low of 815,000 square miles in early March 2017, according to analysis by the National Snow and Ice Data Center in Boulder, Colo.

“It’s really unprecedented,” said Marilyn N. Raphael, a professor of geography at the University of California, Los Angeles, who studies Antarctic sea ice. Warmer ocean temperatures may play a role, she said, “but there are other factors that we’ll be working to figure out in the coming months.”

Antarctic sea ice levels vary widely from year to year, but have generally increased very slightly, on average, since the late 1970s, when satellite observations began. By contrast, sea ice in the Arctic, which is warming three times faster than other regions, has fallen by more than 10% in a decade over the same period.

Two very different domains. The Arctic Ocean covers high latitudes, including the North Pole, and is bordered by land masses. In the Southern Hemisphere, Antarctica covers the pole. The Southern Ocean, which surrounds the continent, begins at much lower latitudes and opens up north.

While rapid warming in the Arctic is largely responsible for the shrinking of sea ice there, the effects of climate change on Antarctic sea ice are much less obvious.

Edward Blanchard-Wrigglesworth, a climate scientist at the University of Washington, says that many scientists expect that global warming will eventually lead to a decline in Antarctic sea ice. But right now, he said, “it’s really hard to connect the two, especially for single events like this one.”

Instead, a complex set of factors is emerging when it comes to Antarctic sea ice. Large-scale atmospheric patterns, often occurring far from the continent, as well as localized winds and ocean currents can all increase or decrease sea ice cover.

For instance, Dr Blanchard-Wrigglesworth said, some studies suggest that a strong El Niño in 2015 and 2016, when sea surface temperatures in the tropical Pacific were higher than normal, led to Sea ice cover was significantly lower in 2016.

Ted Scambos, a senior research fellow at the Center for Earth Science and Observation at the University of Colorado, said in an email that warmer-than-normal sea surface temperatures in some areas around Antarctica could play a role in the current minimum.

And Dr Raphael said winds could also have an influence, particularly in the Amundsen Sea region to the west of the continent. An area of ​​frequent low-pressure air that develops over the sea is particularly strong this year, she said, and that leads to stronger winds that could push more ice farther north, into warmer waters, where it will melt faster.

While the overall sea ice area has increased only slightly since the late 1970s, the rate of increase began to accelerate in 2000, and the amount of ice hit a record high in 2014. But then something unexpected happened. happened, Dr. Raphael said. It plummeted over the next three years, reaching a record low in 2017.

Since then, sea ice extent has rebounded, returning to near-average levels by 2020, Dr Raphael said.

Often, she says, levels will then continue to be average or above average for several years. But the new sharp drop this year came earlier. “It happened so fast,” she said.

“That’s what makes this unusual,” she added. After 2017, “the ice returned to normal but did not stay that way.”

Dr Blanchard-Wrigglesworth said that to understand why ice levels are so low now, researchers will have to examine how conditions might have changed last year. “I wouldn’t be surprised if we found out that this is the result of changes in winds over the past three to six months,” he said.

Low levels of sea ice have been noticed in the Weddell Sea, east of the Antarctic Peninsula, because its circular currents retain more ice year after year than in other parts of the Antarctic coast. A team of scientists and explorers encountered relatively light ice conditions while venturing into the ocean this month search for the wreck of EnduranceErnest Shackleton’s ship, sunk during an Antarctic expedition in 1915.

Ice levels could drop even lower this year, depending on the weather, but should soon start to rise as temperatures begin to drop as the Antarctic fall and winter move. Ice cover peaks each year around the end of September. The average four-decade maximum is more than 7 million square miles.

Dr Blanchard-Wrigglesworth says that events like this one and the previous record lows have provided an opportunity for researchers to better understand the link between climate change and Antarctic sea ice. “A valid new research question might be, are these some of the first signs that a reversal in long-term trends is starting?” he say.

https://www.nytimes.com/2022/02/23/climate/antarctica-sea-ice-arctic.html Sea ice around Antarctica hits record low

Fry Electronics Team

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