The Mystery of the Gaping Hole in Antarctica Finally Revealed

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Jakarta –

The final piece of the puzzle that has puzzled scientists for decades has finally been revealed.

In winter, in the ice sheet above Antarctica’s Weddell Sea, near a submerged peak called Maud Rise, a large hole sometimes opens and gapes, revealing the dark, cold waters beneath.

The hole was first spotted in 1974, and it doesn’t appear every year, leaving scientists wondering about the specific conditions needed to create it.

In the years since the holes resurfaced in 2016 and 2017, solutions have slowly begun to emerge. Using a combination of satellite imagery, floating autonomous instruments, and computational modeling, the answer to this mystery was finally found, and it all involves wind dragging layers of water to create something called an Ekman spiral.

“Ekman transport is an important missing element that is needed to improve the salt balance and maintain the mixing of salt and heat towards the surface of the water,” said oceanographer Alberto Naveira Garabato from the University of Southampton in England, quoted from Science Alert, Friday (3/5/2024 ).

Holes in Antarctic sea ice, known as polynyas, are often seen near shore, used as windows by marine mammals such as seals and whales to catch their breath.

In areas farther out to sea, it is much rarer. In fact, a recurring hole known as the Maud Rise polynya has baffled scientists since it was first seen in satellite images half a century ago.

In 1974, the giant hole was the size of New Zealand. It reappeared in 1975 and 1976, although after that it returned only briefly and weakly, until scientists suspected it would be gone forever. Then, in 2016 and 2017, he returned again.

The Maud Rise polynya in 2017 marked the largest and longest-lasting example of the phenomenon since the 1970s, so scientists got to work. A compilation of data gathered from the sources mentioned above shows that a number of different factors contribute, and they all need to be arranged in the right way to produce a polynya.

One factor was the circular current around the Weddell Sea which was very strong in 2016 and 2017, which resulted in the rise of warm water, especially salt water.

“This upwelling helps explain how sea ice can melt,” explains oceanographer Fabien Roquet of the University of Gothenburg in Sweden.

“But when the sea ice melts, this causes the water surface to become fresh, which in turn stops the mixing. So, other processes have to happen for the polynya to survive. There has to be added salt from somewhere,” he said.

Salt can significantly lower the freezing point of water, so if the water in the polynya is very salty, this could explain why the hole remains. So, the team went back to the data, as well as computational models of the ocean, to figure out where the extra salt came from.

They determined that turbulent eddies produced when the Weddell Current flows around the Maud Rise transport salt to the top of the seamount.

From there, Ekman transportation takes over. This happens when the wind blows over the sea surface, causing resistance. The water is not only pulled, but also deflected sideways like a wake on a boat, causing the water to rotate like a screw. As the top layer of water moves away with the wind, water rises from below to replace it.

In the case of the Maud Rise polynya, this rising water carries with it a buildup of salt that floats around Maud Rise, keeping the hole from freezing.

This key could help scientists predict what will happen to Antarctic sea ice in the future, which is a matter of great concern for the global climate. Climatologists have predicted that winter winds in Antarctica will become stronger and more frequent, so that there will be more polynya winds in large numbers in the coming years.

In turn, this could impact the world’s oceans. “Traces of polynyas can remain in the water for several years after they form,” says climatologist Sarah Gille of the University of California San Diego.

“They can change the way water moves and currents carry heat towards continents. The waters that form here can spread throughout the global ocean,” he concluded.

Watch the Video “The Antarctic and Greenland Ice Sheets Are Melting 3 Times Faster”

(rns/fay)