They discover the mystery of "polinias", the big holes that are in the middle of the Antarctic ice

In the ice on the surface of the Weddell Sea in Antarctica, huge holes were recorded three years ago, which aroused great curiosity among scientists.

Although even larger gaps were formed decades ago, it was the first time that oceanographers had the opportunity to badyze them in depth. And thanks to a new study They discovered his mysterious origin.

Research conducted by the University of Washington (UW) has badociated satellite images of sea ice cover with robotic dinghies and even seals equipped with sensors to better understand the phenomenon.

The results, published in the journal Nature, they determined why they would only appear in a few years and what role they could play in the ocean circulation as a whole.

"We thought this big hole in the pack ice, known as polynya, was something weird, maybe a process that had gone out, but the events of 2016 and 2017 forced us to revise it. ", explained the main author Ethan Campbell, student. PhD in oceanography.

Observations have shown that these gaps open up due to a combination of factors. One of them was the unusual situation of the ocean and the other a series of very intense storms that have invaded the Weddell Sea with almost hurricane winds.

A polynya, a Russian word that roughly means "hole in the ice", can form near the coast when the wind pushes the ice. But it can also appear far from the coast and stay there for weeks or months, where it acts as An oasis for penguins, whales and seals.

The most important known in this region of Antarctica were in 1974, 1975 and 1976, just after the launch of the first satellites, when an area the size of New Zealand remained ice-free during three consecutive winters, despite high temperatures. the air well below the freezing point.

Campbell joined UW as a graduate student in 2016 to better understand this mysterious phenomenon. In a stroke of scientific luck, a big one appeared for the first time in decades.

The new study used observations from the Carbon and Southern Ocean Modeling and Observation Project (SOCCOM), which provides current derivative instruments to monitor Antarctic conditions. He also used data from the Argo Ocean Observing Program, elephant seals that transmit data to the coast, weather stations and decades of satellite imagery.

"The results showed that this polynya is actually caused by a series of factors that all must align to make this happensaid co-author Stephen Riser, professor of oceanography at the University of Washington.

Research has shown that when the winds around Antarctica approach the coast, they favor greater mixing in the East Weddell Sea. In this region, an underwater mountain called Maud Rise forces the dense seawater around it and leaves a rotating vortex at the top.

When the surface of the ocean is particularly salty, as seen throughout 2016, heavy winter storms can trigger a tipping over in traffic. The hottest and saltiest water in the depths is brewed on the surface, where the air cools it and makes it denser than the one below.
When the water drops, a relatively warm water of about 1 degree Celsius replaces it, creating a feedback loop where the ice can not be replenished.

Under the effect of climate change, fresh water from melting glaciers and other sources will make the surface layer of the Southern Ocean less dense, which could mean less of pollinates in the future. But the new study challenged this hypothesis.

Many models show that the winds that surround Antarctica they will become stronger and closer to the coast. The new document suggests that this would encourage the formation of more pollinates, not less.

"At this time, it is thought that most of the bottom waters form on the Antarctic Plateau, but these large marine pollinators they could have been more common in the past. We need to improve our models to be able to study this process, which could have broader climatic consequences, "said Riser.