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Huge holes in the Antarctic sea ice appear for weeks at a time – and scientists might finally know why.
According to a new study, the gaps, which can each cover an area the size of Switzerland, are due to bad weather and underwater vortices.
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Experts know the mysterious ice holes, called polynyas, for decades.
They stay for weeks or even months, where they act as an oasis for penguins, whales and seals to appear and breathe.
The biggest record ever recorded appeared off the Antarctic coast in September 2017 and spread over 19 000 km 2.
Between 1974 and 1976, an area the size of New Zealand was missing in the Antarctic ice floe because of several huge polynyas that developed at the same time.
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Despite many satellite observations, scientists have long wondered how they are formed.
Researchers at the University of Washington, USA, have now solved the problem using state-of-the-art sensors.
Attached to floating robots and even to elephant seals, the equipment tracked weather conditions and ocean conditions around the Weddell Sea in Antarctica.
The researchers found that several factors play a key role in Polynesia's formation – but they must all be present at the same time.
The high wind speed during strong storms displaces the ice and forces upward water brewing in the east of the Weddell Sea.
In this region, an underwater mountain called Maud Rise forces water around her and leaves a rotating vortex above.
The analyzes show that when the surface water is particularly salty, heavy winter storms can trigger a traffic reversal.
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The warmer, more salty water from the depths rises to the surface, creating a feedback loop where the ice can not reform.
"This study shows that this polynya is actually caused by a number of factors that must all align to make this happen," said scientist Stephen Riser.
"Every year, many of these things could happen, but unless you have them all, you do not get polynya."
The study was published in the journal Nature.
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Moreover, Antarctica is becoming scarce at an extraordinary rate, experts revealing that 100 meters thick icecap had disappeared since the 1990s.
Another recent study on permafrost has shown that diseases that were sleeping in old ice may soon become rampant due to climate change.
And, scientists have warned that two thirds of the ice in the Alps will melt by 2100.
What do you think of the huge ice holes? Let us know in the comments …
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