Brain Booster for UPSC & State PCS Examination (Topic: ‘Southern Ocean’ as World’s Fifth Ocean)

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‘Southern Ocean’ as World’s Fifth Ocean

On June 8, 2021 - World Oceans Day- the National Geographic Society has recognised the ‘Southern Ocean’ as the world’s fifth ocean.
The other four oceans are - the Atlantic, Pacific, Indian, and Arctic Oceans.

The IHO too had recognised ‘Southern Ocean’ as a distinct body of water surrounding Antarctica in 1937 but had repealed the same in 1953.
However, the United States Board on Geographic Names as well as the National Oceanic and Atmospheric Administration, both recognize the term ‘Southern Ocean’.

The Southern Ocean is home to large populations of whales, penguins and seals.
But industrial fishing on species like krill and Patagonian toothfish had been a concern for decades.
The recognition would draw attention to these issues, in addition to the rapid warming of the Southern Ocean due to global warming by officially changing the name of the waterbody.

The Southern Ocean is the only ocean ‘to touch three other oceans and to completely embrace a continent rather than being embraced by them’.
It is also defined by its Antarctic Circumpolar Current (ACC) that flows from west to east around Antarctica.
Scientists think the ACC was created 34 million years ago when the continent of Antarctica separated from South America, allowing water to flow unimpeded around the "bottom" of the world.

ACC is the only current in the global ocean to close upon itself in a circumpolar loop.
ACC is also the strongest ocean current on our planet.
This trait makes the ACC the most important current in the Earth’s climate system because it links the Atlantic, Pacific and Indian Oceans and is the primary means of inter-basin exchange of heat, carbon dioxide, chemicals, biology and other tracers.
The ACC is created by the combined effects of strong westerly winds across the Southern Ocean, and the big change in surface temperatures between the Equator and the poles.
Ocean density increases as water gets colder and as it gets more salty. The warm, salty surface waters of the subtropics are much lighter than the cold, fresher waters close to Antarctica. We can imagine that the depth of constant density levels slopes up towards Antarctica.
The westerly winds make this slope steeper, and the ACC rides eastward along it, faster where the slope is steeper, and weaker where it’s flatter.