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How big the holes in the Antarctic ice are, even though it's cold



This is an Inside Science story.

(Inside Science) – By analyzing data from seal robots and sensors glued to seals, researchers can now understand the mysterious origins of giant holes that can open in Antarctic sea ice, according to a new study.

A Polynya – a Russian word meaning "hole in the ice" – can form off the coast of the Antarctic and serve as a sanctuary for penguins, whales and seals for weeks or even months. The largest known Polynyas in the winter sea ice of the Antarctic Weddell Sea appeared shortly after the launch of the first satellites. For the three consecutive winters from 1

974 to 1976, New Zealand's area remained ice-free, even though air temperatures were far below freezing.

The rarity of the great Polynyas in Antarctic waters meant that little was known about how these holes could form in bitter cold. But in 2016, for the first time in decades, a large Polynya surfaced, an area of ​​33,000 square kilometers that remained open for three weeks. An even larger 50,000 square kilometer polyny appeared in September and October 2017.

Scientists studied decades of satellite images of sea ice cover and data from Antarctic weather stations and collected data from robots glued to sea elephant seals in currents in the Southern Ocean and even sensors. They found these Polynyas formed when the cold surface water was also particularly salty. This salt content made it denser and therefore rather mingled with similar salty and denser water.

<img src = "https://s.abcnews.com/images/Technology/inside-science-polynya-02-ht-jc-190611_hpMain_4x3_992.jpg" border = "0" width = "640" height = "480" alt = "PHOTO: The hole in the sea ice off the Antarctic coast as seen by a NASA satellite on September 25, 2017. [19659007] NASA
The hole in the sea ice off the coast of the Antarctic, on the September 25, 2017 from a NASA satellite.

Heavy storms that swirled across the Weddell Sea with almost hurricane-like winds whirled relatively strong warm water from the deep ocean, melting ice and opening polynyas in the sea ice. As this water cooled, it became denser and more likely to sink in. From below, warmer water swelled to replace it, creating a heat circulation that kept the polynyas open.

"The deep ocean is generally a quiet place in which changes take place slowly, but we stel During his relatively short period of time, he noted that he was moved hard by polynya events, "said study leader Ethan Campbell, a physical oceanographer at the University of Washington in Seattle.

Under climate change, freshwater from melting Antarctic ice sheets would make the surface waters of the Southern Ocean less dense, leading to fewer Polynyas in the future. On the other hand, many climate models suggest that Antarctic winds are getting stronger and moving closer to the coast, potentially creating more polynyas.

Scientists published their findings online on June 10 in the journal Nature.

Inside Science is an editorially independent nonprofit news service for print, electronic and video journalism owned and operated by the American Institute of Physics.

  PHOTO: Inside Science
Inside Science

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