The Antarctic Circumpolar Current (ACC), the only ocean current that circumnavigates the planet, is speeding up. For the first time, scientists are able to tell that this is happening by taking advantage of a decades-long set of observational records.
The ACC separates the Southern Ocean that surrounds Antarctica from the Atlantic, Pacific, and Indian Oceans and carries water clockwise around the globe.
It is arguably the mightiest of all the ocean currents, and extends from the sea surface to depths of 2000-4000 meters, (up to 13,123 feet) and can be as wide as 2000 kilometers (1,243 miles).
Historically, the ACC has been referred to as the ‘West Wind Drift’ because the prevailing westerly wind and current are both eastward.
Researchers from Scripps Institution of Oceanography at UC San Diego, Woods Hole Oceanographic Institution, the Chinese Academy of Sciences, and UC Riverside were able to determine that “robust acceleration” in the ACC was driven mostly by human activity, which has caused ocean temperatures to climb.
The research team used satellite data on the height of the sea surface and data collected by Argo floats, data-gathering robotic instruments in oceans all over the world used to track the temperature and salinity of ocean water.
That network of autonomous floats, which measure ocean conditions such as temperature and salinity, began in 1999 and reached full capacity in 2007. A full complement of 4,000 floats across the world’s oceans continues to collect data to this day.
The team representing the National Science Foundation-funded Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project reported its findings in the Nov. 29 issue of the journal Nature Climate Change.
“From both observations and models, we find that the ocean heat change is causing the significant ocean current acceleration detected during recent decades,” said Jia-Rui Shi, formerly a Ph.D. student at Scripps Oceanography and currently a postdoctoral researcher at Woods Hole Oceanographic Institution, according to Science Daily.
“This speedup of the ACC, especially its jet centered on the Subantarctic Front, facilitates property exchange, such as of heat or carbon, between ocean basins and creates the opportunity for these properties to increase in subsurface subtropical regions.”
It is important that scientists understand the dynamics of what happens when the amount of heat difference between warm and cold waters increases, and currents between those two masses speed up.
“The ACC is mostly driven by wind, but we show that changes in its speed are surprisingly mostly due to changes in the heat gradient,” said co-author Lynne Talley, a physical oceanographer at Scripps Oceanography.
