Since 1974, a hole roughly the size of Switzerland has periodically opened in the Antarctic ice. The Maudrise polynya (the geographical name for the area of open water surrounded by sea ice) was discovered in the Weddell Sea 50 years ago and has been opened several times since, though not always at the same time, but always in the same place. This has caused a serious headache for researchers, writes A Live sciences.
In the winter of 2016 and 2017, it was opened to a width of approximately 80,000 square kilometers for several weeks, and then it was finally possible to reveal what explains this phenomenon.
In winter, the area of Antarctica's ice increases sixfold, but holes are formed in the sea ice due to strong winds coming from the ground, which freeze the water in the holes. But in the open ocean, away from coastal winds, there are less likely to be gaps in sea ice, where, for example, the Maud High is formed.
It found that in 2016 and 2017, the ocean eddy current in the Weddell Sea was stronger than in other years, making it easier for underwater movements to bring salt and heat closer to the surface. The hole, which opens from time to time, is located near an underwater mountain. During the fateful two years, salt was deposited on the mountain due to the strong current, and winds buffeted the surface, drawing in the saltiest water. This salt lowered the freezing point of surface water, so a crater could form and remain open for a period of time.
Climate change is already making winds from Antarctica stronger, and we can expect more holes in the future. These polynyas can change the movement of water and the transfer of heat by currents towards the continents. 40% of the world's ocean water comes from the Antarctic coast, which is vital for regulating the planet's climate.
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