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Why Antarctic sea ice is retreating faster than it is forming

New research explains why the sea ice around Antarctica is retreating faster than it is advancing.

In the southern hemisphere, the ice cover around Antarctica gradually expands from March to October each year. During this period, the total ice area increases 6 times and becomes larger than Russia.

“…I was surprised that the rapid seasonal retreat of Antarctic sea ice could be explained by such a simple mechanism.”

Sea ice then retreats more rapidly, most dramatically in December when Antarctica has constant daylight.

The new study finds that unlike other aspects of its behavior, Antarctic sea ice follows only simple rules of physics.

“Despite the puzzling longer-term trends and large year-to-year variability in Antarctica sea ​​icethe seasonal cycle is really consistent and always shows this fast retreat relative to slow growth,” says lead author Lettie Roach, who conducted the study as a postdoctoral researcher at the University of Washington and is now a research scientist at NASA and Columbia University.

“Given the complexity of our climate system, I was surprised that the rapid seasonal retreat of Antarctic sea ice could be explained by such a simple mechanism,” says Roach.

Previous studies examined whether wind patterns or warm ocean water could be responsible for the asymmetry in Antarctica’s seasonal sea-ice cycle.

But the new study shows that just as a hot summer day peaks in the late afternoon, a sizzling state sets in Antarctic summer peaks in melting in midsummer, accelerating warming and sea ice loss, with slower changes in temperature and sea ice when solar radiation is low during the rest of the year.

The researchers examined global climate models and found that they reproduced the faster retreat of Antarctic sea ice. They then built a simple physics-based model to show that the reason is the seasonal pattern of incoming solar radiation.

Near the North Pole, Arctic ice cover has gradually decreased with global warming since the 1970s. However, Antarctica’s ice cover has shifted back and forth in recent decades. Researchers are still working to understand the sea ice around the South Pole and better represent it in climate models.

“Antarctic sea ice is behaving as we should expect, and the Arctic seasonal cycle is more mysterious.”

“I think because we normally assume that Antarctic sea ice is enigmatic, previous studies assumed that the rapid seasonal retreat of Antarctic sea ice was also unexpected — in contrast to the Arctic, which has seasons of ice advance and retreat.” are more similar,” Roach says.

“Our results show that the seasonal cycle in Antarctic sea ice can be explained with very simple physics. In terms of the seasonal cycle, Antarctic sea ice is behaving as we should expect, and the Arctic seasonal cycle is more mysterious.”

Researchers are now investigating why Arctic sea ice does not follow this pattern, instead growing slightly faster over the Arctic Ocean each year than it is retreating. Because Antarctica’s geography is simple, with a polar continent surrounded by ocean, this aspect of sea ice might be simpler, Roach says.

“We know them Southern Ocean plays an important role in the Earth’s climate. Being able to explain this key feature of Antarctic sea ice, which has been wrong in standard textbooks, and showing that the models reproduce it correctly, is a step towards understanding this system and predicting future changes,” says co-author Cecilia Bitz, Professor of Atmospheric Sciences.

The study was published in nature geosciences. Additional co-authors are from the Scripps Institution of Oceanography, the University of Wisconsin-Madison and the University of Washington.

The work was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration and the UK-based Scientific Committee on Antarctic Research.

Source: University of Washington

https://www.futurity.org/antarctica-sea-ice-2720132-2/?utm_source=rss&utm_medium=rss&utm_campaign=antarctica-sea-ice-2720132-2 Why Antarctic sea ice is retreating faster than it is forming

Dais Johnston

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