Antarctica's Hole Keeps Opening Due To Salt Lowering Freezing Point, Experts Say

Experts said that Antarctica's hole, which is a size of the country Switzerland, has been cracking open ever since.

In a study, they found out that the open-ocean polynyas formed over the Maud Rise, which is situated in the Weddell Sea, during the winter period of 2016 to 2017.

Open-Ocean Polynyas

Researchers first spotted the hole in 1974 and 1976 in Antarctica's Weddell Sea, and since then it has reappeared fleetingly based on observations.

Scientists suggested that such polynyas are considered to be rare events in the Southern Ocean and they are often associated with deep convection that may affect regional carbon and heat budgets.

Through the use of an ocean state estimate, researchers have discovered that during 2017, the early sea ice melting had transpired in response to enhanced vertical mixing of heat.

This phenomenon was accompanied by mixing of salt.

Experts pointed out that the melting sea ice compensated for the vertically mixed salt and this resulted in a net buoyancy gain. Further, an additional salt input was then significant to destabilize the upper ocean.

Studies said that this came from a hitherto unexplored polynya-formation mechanism or an Ekman transport of salt across a jet girdling the northern flank of the Maud Rise.

Researchers explained that such transport was driven by intensified eastward surface stresses during 2015 to 2018.

''Our results illustrate how highly localized interactions between wind, ocean flow and topography can trigger polynya formation in the open Southern Ocean,'' experts said.

Based on study, polynyas are openings in the sea ice during winter that usually expose relatively warm ocean waters to a much colder atmosphere. This will later result in large heat fluxes that cool the water column and can sustain deep vertical convection that ventilates the ocean interior.

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Regular Occurences

It was explained that coastal polynyas along the Antarctic margins are regular occurrences and are formed by strong katabatic winds that push sea ice away from the coast.

In contrast, open-ocean polynyas in the Southern Ocean are rare events and these are often associated with surface salinity anomalies that initiate deep convection.

Experts noted that such convection connects the mixed layer with the warmer circumpolar deep water, which is found at relatively shallow depths of 200 to 500 m within the gyres of the subpolar Southern Ocean.

Because of the stronger current, salt hovered around the seamount while the wind blew over the surface, which created a corkscrew effect.

This motion then dragged the saltier water around the submerged mountain to the surface. The said salt then lowered the freezing point of the surface water, enabling the Maud Rise polynya to form and persist.

Experts pointed out that the latest discovery is vital for understanding Antarctica and its broader impacts on the global ocean.

They explained that climate change is already making winds from the southernmost continent more powerful, and this will likely create more polynyas in the future.

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