For decades, scientists have believed that the leakage of warm, salty Indian Ocean water south of South Africa into the Atlantic—known as Agulhas Leakage—is a major contributor to the Atlantic Meridional Overturning Circulation (AMOC), a key component of the global ocean conveyor belt. However, a new study published in Nature Communications on July 30, 2026, presents geological evidence that questions this long-held assumption.
The research team, led by Dr. Ian Hall from Cardiff University, analyzed sediment cores from the Cape Basin off the coast of South Africa. These cores provide a record of ocean conditions over the past 1.2 million years. By examining the chemical signatures of plankton and other organic matter, the team reconstructed the history of Agulhas Leakage and compared it with records of AMOC strength.
The findings reveal that periods of strong Agulhas Leakage do not consistently correspond with periods of strong AMOC. In fact, during some intervals, increased leakage coincided with a weaker AMOC, contradicting the conventional view that more leakage leads to a stronger overturning circulation. This suggests that the relationship between Agulhas Leakage and AMOC is more complex than previously thought.
The authors caution that their results do not dismiss the importance of Agulhas Leakage entirely, but they indicate that other factors, such as wind patterns and freshwater input, may play a more significant role in regulating AMOC. The study has implications for predicting how AMOC might respond to future climate change, as current models may overestimate the influence of Agulhas Leakage.
This research adds to a growing body of evidence that challenges simplistic views of ocean circulation, highlighting the need for more nuanced models to project future climate scenarios.
