The findings have important implications for global climate change. The study suggests that intensifying winds in the region may be increasing the turbulence of the current, rather than increasing its flow rate.
One of the strongest currents in the world, the Agulhas Current flows along the east coast of South Africa, sending warm, salty water away from the tropics toward the poles. The Agulhas, which is hundreds of kilometers long and over 2,000-meters deep, transports large amounts of ocean heat and is considered to have an influence not only on the regional climate of Africa, but on global climate as part of the ocean’s global overturning circulation.
Boundary Current Changes
Lead author Lisa Beal, a UM Rosenstiel School professor of ocean sciences, said:
“Changes in western boundary currents could exacerbate or mitigate future climate change. Currently, western boundary current regions are warming at three times the rate of the rest of the world ocean and our research suggests this may be related to a broadening of these current systems.”
Using measurements collected during three scientific cruises to the Agulhas Current, the Indian Ocean’s version of the Gulf Stream, researchers estimated the long-term transport of the current leveraging 22 years of satellite data. They found the Agulhas Current has broadened, not strengthened, since the early 1990s, due to more turbulence from increased eddying and meandering.
Study co-author Shane Elipot, a UM Rosenstiel School associate scientist, said:
“To find decades of broadening, rather than intensification, profoundly impacts our understanding of the Agulhas Current and its future role in climate change. Increased eddying and meandering could act to decrease poleward heat transport, while increasing coastal upwelling and the exchange of pollutants and larvae across the current from the coast to the open ocean.”
Previous studies have suggested that accelerated warming rates observed over western boundary current regions, together with ongoing strengthening and expansion of the global wind systems predicted by climate models relate to an intensification and pole-ward shift of western boundary currents as a result of man-made climate change.