Antarctica still hides many mysteries, which scientists are working hard to unravel. A study published this 1er May in the journal Science Advances lifts the veil on one of them: the fascinating “hole” of Maud Rise, named after the oceanic plateau in the region.
The continent is dotted with holes in the ice, called “polynyas”, used in particular by marine mammals as small spaces for breathing. Most of the time, these holes are observed near shorelines. A gigantic hole is an exception, the famous Maud Rise polynya.
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It was first observed in 1974 and does not appear every year, ScienceAlert says. Virtually disappeared for several decades, it reappeared without warning in 2016, then in 2017. A comeback: its size suddenly increased from an area of 9,500 square kilometers to 80,000 square kilometers in just one month – a growth of 740%… That’s more than twice the size of Belgium! He comes and goes, and the scientists didn’t understand anything about it. Till today.
The latest study on the subject provides an explanation for this strange phenomenon. Using satellite images, floating objects and even seals wearing hats to collect data, the verdict is in: it’s all Ekman’s fault. Or rather, the Ekman spiral.
Weddell currents and Ekman spiral
It’s actually a whole process that lines up perfectly to create this polynya. First, the circular currents of the Weddell Sea cause an upwelling of warm water. This rise melts the ice pack, which then cools the water on the surface, leading to a vicious circle. But that’s not all.
Weddell currents also bring large quantities of salt to the surface, which significantly lowers the freezing point of water. Enough to create this huge hole? Not yet.
The Ekman spiral then takes over. When the wind blows across the surface, water can be pushed sideways, creating this famous spiral. By pushing the upper layers of water away, the wind brings up deep water. This is always saltier than the surface water. Salt then builds up around the Maud Rise polynya, preventing the water from freezing and the hole from closing.
This discovery allows scientists to better understand ice fluctuations in Antarctica. But she doesn’t bring good news. According to climatologists, the continent’s winter winds could be increasingly strong and frequent, multiplying the number of polynyas and transforming the area into a veritable icy Swiss cheese.
