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 reappeared fleetingly and sporadically — opening up to different sizes but in the same place, and sometimes not appearing at all for years. This has left scientists confused about the exact conditions needed for the hole to form.
In 2016 and 2017, a massive 309,000 square miles (80,000 square kilometers) opened up for several weeks during the winter, enabling scientists to take a closer look at the phenomenon and solve the 50-year-old mystery. They reported their findings on Wednesday (May 1) in the journal Advancement of science.
“2017 was the first time we had such a large, long-lived polynya in the Weddell Sea since the 1970s,” lead author Aditya Narayanana postdoctoral researcher at the University of Southampton in England, He said in asRatement.
As summer turns to winter in Antarctica, sea ice expands from a minimum of about 1 million square miles (3 million square km) to 7 million square miles (18 million square km)4% of the floor surface 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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These cold winds also freeze more seawater within the polynya, adding additional chunks to the ice layer.
But in the open ocean, away from these coastal winds, where Maud Rays polynyas form, holes in the sea ice are less likely. This, in addition to A A striking reduction in total ice extent Across the Southern Ocean, it has led scientists to wonder what specific conditions could cause polynya mudrays to form.
Antarctic sea ice decline
To investigate the mystery, scientists studied data from satellites, autonomous buoys, and tagged marine mammals, as well as previous observations made by 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 the stronger current, salt swirled around this seamount as winds blew on the surface, creating a spiral effect that pulled saltwater around the submerged mountain to the surface. This salt then lowered the freezing point of surface water, enabling polynya mudrise to form and persist.
The new discovery is important for understanding Antarctica and its broader impacts on the global ocean, according to the researchers. Climate change is already causing winds 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 global ocean water It finds its origins in the coast of Antarctica, making it vital in regulating regional climates throughout 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 carry heat toward 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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