Agulhas Current animation (blog post)
The physical oceanography component of NASA’s Jet Propulsion Laboratory in Pasadena, California, has made available this fascinating animation of the Agulhas Current. Based on satellite data for sea surface temperature, it reduces the three-year period from the beginning of 2011 to the end of 2013 to just one and a half minutes.
The Agulhas Current is a western boundary current – located at the west side of an ocean basin – that flows southward along South Africa’s east coast. It is considered the Indian Ocean’s version of the Gulf Stream on the Atlantic coast of the USA, although that flows northward, since all western boundary currents carry warm water from the tropics poleward.
The Agulhas Current follows the continental shelf to the tip of Africa, off Cape Agulhas, where it turns back on itself, or retroflects, to form the Agulhas Return Current. However, some of its water escapes as eddies, filaments or so-called Agulhas rings – pinched off at the retroflection area - into the Atlantic Ocean. This ‘Agulhas leakage’ of warm, salty water is thought to play an important role in global ocean circulation, also known as thermohaline circulation or the ocean conveyor belt, which is largely driven by density gradients.
This is the reason for the considerable international interest and research attention focussed on the Agulhas Current in recent years. By influencing oceanic heat transport and uptake of atmospheric carbon dioxide, Agulhas leakage may have a major effect on climate change. What’s more, there’s evidence to suggest that the Agulhas Current has warmed by as much as 1.5°C since the 1980s, and that its leakage into the Atlantic Ocean has increased with global warming.
On a regional scale, the Agulhas Current is known to have a strong influence on the sub-continent’s rainfall patterns, and has been linked to extreme weather events on the southern and eastern coasts. Evaporation results in high levels of water vapour in the air above the Agulhas Current, often seen as a band of cloud on satellite images. This moisture can be advected onshore to fuel storms and tornadoes.