Researchers have discovered the missing piece of the puzzle related to a rare break in the sea ice around Antarctica that occurred in the winter of 2016 and 2017. It reveals an important process that has eluded scientists: how this hole, called a polynya, can form and last for several weeks. The results of the research were published May 1 in the scientific journal Science Advances.
The polynya that has eluded researchers is called Maud Rising and sometimes forms above the seamount of the same name in Antarctica’s Weddell Sea. Over the years the Maud Rise polynya has formed only occasionally and for a limited time, but in 2016 and 2017 it grew to the size of Switzerland.
“We now understand that polynya results from a complex interaction between the unique geography of the ocean floor and extremely strong winds that create extremely strong ocean currents that transport heat and salt water to the surface. But it also required the involvement of a very specific key process,” says the University of Gothenburg’s School of Marine Sciences. Fabien Roque, Professor of Physical Oceanography and one of the researchers behind the discovery.
Detective work to find the missing piece
Shrubs are important sites that help moderate atmospheric carbon dioxide increases and support increased biological activity in sea ice-covered areas. They usually form in coastal areas when strong coastal winds blow across the continent and push the ice, exposing the underlying seawater. But sometimes they can also form in sea ice over the open ocean when warm water is brought to the surface by ocean currents, as during Maud’s rise.
“This upward flow of warm water explains how sea ice can melt. But when sea ice melts, it leads to a freshening of surface waters, which stops the upward flow. So for the polynyas to persist, another process must occur. At the National Oceanography Center (UK) Aditya Narayanan, researcher and lead author of the study, says there must be additional salt entering from somewhere.
Salt was brought to the region through a special process
Researchers began detective work to figure out where the extra salty seawater was coming from. They used remotely sensed maps of sea ice, observations from autonomous buoys and tagged marine mammals, and a computer model of the state of the ocean.
They found that when the extremely powerful Weddell Sea Current flows around the Maud Rise, turbulent eddies transport salt to the top of the seamount. From here, a process called “Ekman transport” helped transport salt to the northern flank of the Maud Rise, where the polynya first formed. Named after Swedish oceanographer Vagn Walfrid Ekman, who pioneered the study of how wind creates ocean currents, Ekman transport is a very special process in which water affects the ocean by moving at a 90-degree angle to the direction of the wind blowing from above. currents.
“The Eckmant transport was an important missing piece of the puzzle; it was needed to increase the salt balance and promote the mixing of salt and heat into the surface waters,” says Fabien Roque.
Sage trees are important for climate
The effects of polynyas can persist in the oceans for years, even after their formation. They can change the movement of water and how currents transport heat to the continent. The dense waters formed here can spread to the world’s oceans.
“Some of the same processes, such as upwelling of deep, salty waters involved in the formation of Maud’s rising polynya, are also driving the overall decline in sea ice in the Southern Ocean,” says UC San Diego Professor Sara Gille. co-author research.
“This is the first time we’ve seen such a large and long-lived polynya in the Weddell Sea since the 1970s,” says Aditya Narayanan.
Source: Port Altele
