An Antarctic ice hole the size of Switzerland continues to burst. Now scientists finally know why.

Scientists have finally discovered why a hole the size of Switzerland repeatedly appears in Antarctica’s sea ice.

The hole, called the Maud Rise polynya, was first discovered by researchers in 1974 and 1976 in Antarctica’s Weddell Sea, and since then it has resurfaced fleetingly and sporadically – opening up to different sizes but in the same place, and sometimes completely not appearing. for years. This has confused scientists about the exact conditions required for the hole to form.

In 2016 and 2017, a vast area of 80,000 square kilometers opened up for several weeks during the winter, allowing scientists to take a closer look at the phenomenon and solve the 50-year-old mystery. They reported their findings Wednesday (May 1) in the journal Progress of science.

“2017 was the first time since the 1970s that we had such a large, long-lived polynya in the Weddell Sea,” says lead author Aditya Narayanana postdoctoral researcher at the University of Southampton in England, He said in asRto eat.

As summer turns to winter in Antarctica, sea ice expands from at least approx 1 million square miles (3 million square km) to 7 million square miles (18 million square km)4% of the floor area is covered with irregular white porcelain tiles.

Most of this sea ice grows during the weeks-long polar night on the floating ice shelves that wrap around the continent. Holes in this ice, called polynyas, form when strong winds from inland push the tiles apart.

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This cold wind also freezes more seawater in the polynya, adding additional chunks to the ice layer.

But in the open ocean, far from these coastal winds, where Maud Rays polynyas form, gaps in the sea ice are less likely. This, next to A A striking reduction in the total ice mass Across the Southern Ocean, scientists have wondered under what specific conditions polynya mud rays can form.

Decline in Antarctic sea ice

To investigate the mystery, scientists studied data from satellites, autonomous buoys and tagged marine mammals, as well as previous observations from other researchers. They found that in 2016 and 2017, the circular ocean current in the Weddell Sea, called the Weddell gyre, was stronger than in other years, making it easier for underwater currents to bring salt and heat closer to the surface.

Maud Rise polynya is located near the underwater mountain Maud Rise. In 2016 and 2017, due to stronger currents, the salt swirled around this seamount as the wind blew across the surface, creating a spiral effect that pulled the saltwater around the submerged mountain to the surface. This salt then lowered the freezing point of surface waters, allowing polynya mud formations to form and persist.

The new discovery is important for understanding Antarctica and its broader impact on the global ocean, according to the researchers. Climate change is already causing wind to blow from the far south of the continent more powerfulThis will likely lead to the creation of more polynes in the future. while, 40% of the world’s ocean water It originates from the coast of Antarctica, making it critical for regulating regional climates across the planet.

“The polynya signature can remain in the water for many years after it forms. It can change how water moves and how currents transport heat to the continent,” study co-author. Sarah Jill“The dense water that forms here could spread across the World Ocean,” the UC San Diego climatology professor said in the statement.

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