Sea ice around Antarctica hits record high

Sea ice around Antarctica has reached an all-time high in four decades of observations, according to a new analysis of satellite images....

Sea ice around Antarctica has reached an all-time high in four decades of observations, according to a new analysis of satellite images.

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

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

Antarctic sea ice extent is highly variable from year to year, but overall has increased very slightly, on average, since the late 1970s when satellite observations began. In contrast, the extent of sea ice in the Arctic, which is warming about three times faster than in other regions, has shrunk by more than 10% in ten years during the same period.

The two regions are very different. The Arctic Ocean covers high latitudes, including the North Pole itself, and is surrounded by landmasses. In the southern hemisphere, Antarctica spans the pole. The Southern Ocean, which surrounds the continent, begins at much lower latitudes and opens to the north.

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

Edward Blanchard-Wrigglesworth, a climatologist at the University of Washington, said many scientists expect global warming to eventually cause Antarctic sea ice to shrink. But right now, he said, “it’s really hard to connect the two, especially in terms of single events like this.”

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

For example, Dr Blanchard-Wrigglesworth said, some research suggests that a strong El NiƱo in 2015 and 2016, when sea surface temperatures in the tropical Pacific were warmer than normal, caused a sharp drop in sea ​​ice cover in 2016.

Ted Scambos, a senior researcher at the University of Colorado’s Earth Science and Observation Center, said in an email message that warmer-than-normal sea surface temperatures in parts of Antarctica may have played a role in the current minimum.

And Dr Raphael said the winds may also have had an effect, particularly in the Amundsen Sea region on the western side of the continent. A region of low-pressure air that develops steadily over the sea has been particularly strong this year, she said, and that has brought stronger winds that may have pushed more ice further. to the north, in warmer waters where they would melt faster.

While global sea ice extent has increased only slightly since the late 1970s, the rate of increase began to accelerate in 2000 and sea ice extent reached a record high in 2014. But something unexpected happened, says Dr. Raphael. It dropped drastically over the next three years, hitting a record low in 2017.

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

Normally, she says, levels would then have continued to be average or above average for several years. But this year’s new sharp drop happened earlier. “It happened so fast,” she said.

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

Dr Blanchard-Wrigglesworth said that to understand why the extent of the ice is so weak now, researchers will need to look at how conditions might have changed last year. “I wouldn’t be surprised if we found out that’s the result of the changing winds over the last three to six months,” he said.

The low extent of sea ice was noticeable in the Weddell Sea east of the Antarctic Peninsula, which, due to its circular current, retains far more ice from year to year than other parts of the Antarctic coast. A group of scientists and explorers encountered relatively mild ice conditions while venturing out to sea this month in search of the wreckage of the EnduranceErnest Shackleton’s ship, which sank during an expedition to Antarctica in 1915.

This year’s ice extent could drop even further, depending on the weather, but should soon begin to increase as temperatures begin to drop as we approach the Antarctic fall and winter. Ice cover peaks each year towards the end of September. The four-decade average maximum is over 7 million square miles.

Dr Blanchard-Wrigglesworth said events like this and the previous record gave researchers the opportunity to better understand the link between climate change and sea ice in Antarctica. “A valid new research question might be, are these the first indications that there is starting to be a reversal in long-term trends?” he said.

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Newsrust - US Top News: Sea ice around Antarctica hits record high
Sea ice around Antarctica hits record high
Newsrust - US Top News
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