The Indian Ocean’s Agulhas Current — one of the strongest currents in the world — is getting wider rather than strengthening, which will have important implications for global climate change, a study says. The findings suggest that intensifying winds in the region may be increasing the turbulence of the current, rather than increasing its flow rate.
“To find decades of broadening, rather than intensification, profoundly impacts our understanding of the Agulhas Current and its future role in climate change,” said study co-author Shane Elipot of the University of Miami’s Rosenstiel School of Marine and Atmospheric Science in the US.
The Agulhas Current flows along the east coast of South Africa, transporting warm, salty water away from the tropics toward the poles.
Using measurements collected during three scientific cruises to the Agulhas Current, the Indian Ocean’s version of the Gulf Stream, the 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.
“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,” Elipot said.
The Agulhas, which is hundreds of kilometres long and over 2,000-metres 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.
“Changes in western boundary currents could exacerbate or mitigate future climate change,” lead author of the study Lisa Beal, also a professor at the Rosenstiel School noted.
“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,” Beal said.