The Antarctic Circumpolar Current, or ACC, is the strongest ocean current on our planet. It extends from the sea surface to the bottom of the ocean, and encircles Antarctica.

It is vital for Earth’s health because it keeps Antarctica cool and frozen. It is also changing as the world’s climate warms.

The ACC carries an estimated 165 million to 182 million cubic metres of water every second  from west to east, more than 100 times the flow of all the rivers on Earth. It provides the main connection between the Indian, Pacific and Atlantic Oceans.

The tightest geographical constriction through which the current flows is Drake Passage, where only 800 km separates South America from Antarctica. While elsewhere the ACC appears to have a broad domain, it must also navigate steep undersea mountains that constrain its path and steer it north and south across the Southern Ocean.

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. A salinity and temperature difference keeps the current hugging Antarctica.

It rises and sinks at various places, These pathways are the main way that the oceans absorb heat and carbon dioxide and sequester it in the deep ocean.

Waters south of the Polar Front are becoming fresher due to increased rainfall there, and waters to the north of the Polar Front are becoming saltier due to increased evaporation. These changes are caused by human activity.

Winds have strengthened by about 40% over the Southern Ocean over the past 40 years. Surprisingly, this has not caused an increase in the strength of the ACC. Instead there has been an increase in eddies that move heat towards the pole.

The question now is how this transfer of heat across the ACC will impact the stability of the Antarctic ice sheet, and consequently the rate of global sea-level rise.

Source  The Conversation