The waters that flow to the bottom of the Southern Ocean, around Antarctica, are colder and deeper than in the rest of the world. In some areas around the continent, sea water is cooled by the especially icy air that envelops the environment, facilitating the formation of ice. When the ice forms, the salt is transferred to the water that still remains in a liquid state making it even more salty.
Thus, these waters, at a lower temperature and with a higher density than normal , end up sinking to the seabed and spreading north. Little by little, they end up spreading through the oceanic depths of the entire world and mixing with the rest of the warmer waters. It is how ocean currents are created and is crucial for the proper maintenance of underwater ecosystems.
Decreasing volume of water
But almost a decade ago, in 2012, oceanographers discovered that large amounts of these waters had been disappearing without apparent explanation. To do this, they reviewed the temperature data collected from 1980 to 2011 at intervals of about ten years and found that the volume of water on the Antarctic bottom had been decreasing at an average rate of about eight million metric tons per second during the last decades. Which is roughly equivalent to about 50 times the average flow of the Mississippi River, according to data from the United States National Oceanic and Atmospheric Administration (NOAA).
The lead author of the study Sarah Purkey , then a graduate student at the University of Washington (United States), remarked that, since the 1980s, the average rate at which the Antarctic bottom water had been reducing had remained fairly stable.
Why this happens is not entirely clear, but the trend could have major repercussions on Earth’s climate, as changes in temperature, the amount of salt in ocean water, and levels of Dissolved oxygen and carbon dioxide in these cold waters play a role in the dreaded rise in sea level .
