Scientists solve mystery of giant hole in Antarctica that was twice the size of New Jersey when it appeared in 2016
Scientists have solved the mystery of how a gaping hole nearly twice the size of New Jersey formed in Antarctica’s sea ice eight years ago.
The rare opening of ice-free water, called a polynya, was first discovered in 1974 and persisted for the next two years until the void finally closed.
Scientists were again baffled in 2016 and 2017 when the polynya reappeared due to its enormous size and distance from shore, sending them on a hunt to discover what formed the hole.
Researchers from the University of Southampton have discovered that the cause was actually a combination of ocean water currents, wind and increasing salinity in the water that caused the sea ice to melt.
The Maud Rise polynya appeared in the winters of 2016 and 2017 and was almost twice the size of New Jersey. Pictured: A satellite image of the polynya in 2017
Scientists first discovered the Maud Rise polynya in 1975 and thought it would be an annual event, but didn’t see it again until more than four decades later. Pictured: Satellite images of the 1975 Maud Rise polynya
The polynya was caused by a combination of ocean water currents, winds and increasing salinity in the water that melted the sea ice.
Scientists named the opening the Maud Rise polynya in the 1970s, after the underwater mountain located below it in the Weddell Sea.
Polynyas typically occur every year in sea ice in the coastal areas of Antarctica, but it is unusual for them to form hundreds of kilometers away in the open ocean, where the sea is thousands of meters deep.
“The Maud Rise polynya was discovered in the 1970s when remote sensing satellites that can see sea ice over the Southern Ocean were first launched,” said Aditya Narayanan, a postdoctoral researcher at the University of Southampton and lead author of the study.
‘It persisted for successive winters from 1974 to 1976 and oceanographers at the time assumed it would be an annual occurrence. But since the 1970s, this has only occurred sporadically and at short intervals,” Narayanan continued.
‘2017 was the first time since the 1970s that we have had such a large and long-lived polynya in the Weddell Sea.’
The researchers set out to discover how the polynya formed so far from shore using remotely sensed sea ice maps, data from tagged marine animals and a computer-generated model of the ocean.
The results showed that the current moving around the underwater Maud Rise Mountain in the Weddell Sea created turbulent eddies – a countercurrent – that moved the salt to the sea surface.
Experts say 2017 (pictured) was the first time since the 1970s that we have had such a large and long-lived polynya in the Weddell Sea.
The appearance of a polynya hundreds of kilometers off the coast of Antarctica is an unusual event and researchers found that it is caused by a combination of water currents, wind and salt. In the photo: the Maud Rise polynya in 2017 In the photo: sea ice in the water at Cuverville Island in Antarctica
Scientists were stunned again in 2016 and 2017 when the polynya reappeared and they set out on a hunt to discover what formed the hole
Once the salt reached the surface, a process called Ekman transport took place, moving the water at a 90 degree angle toward the wind, making it easier for the salt to settle with the heat to mix the surface and melt the ice.
“Ekman transport was the essential missing ingredient needed to increase salt balance and maintain the mixing of salt and heat with surface water,” said Alberto Naveira Garabato, co-author and professor of the study at the University of Southampton.
The researchers speculated that polar cyclones passing through the region could have caused the Ekman transport to be stronger, bringing excess salt to the surface, but clarified that their research could not verify the theory.
Researchers are now warning that the polynyas could have a negative impact on the oceans and contribute to rising sea levels, which have risen by 0.7 cm between 2022 and 2023.
“The print of polynyas can remain in the water for several years after they form,” said Sarah Gille, co-author of the study and professor at the University of California, San Diego, member of the study team.
‘They can change how water moves and how currents transport heat to the continent. The dense waters that form here could spread across the world ocean.”