Nature Geoscience paper: Agulhas Leakage does not always strengthen AMOC
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An international team led by Utrecht University has found geological evidence that the Agulhas Leakage, a transfer of warm Indian Ocean water into the Atlantic, does not always strengthen the Atlantic Meridional Overturning Circulation (AMOC), according to a study published in Nature Geoscience. The finding challenges a decades-long assumption that salty Indian Ocean water is essential for deep-water formation in the North Atlantic. The AMOC remained robust even during periods of weakened leakage, the study shows.
The Long-Held Assumption
For decades, climate scientists assumed that Agulhas Leakage—the transport of warm, saline Indian Ocean water around South Africa into the Atlantic—supplied salt that strengthened the AMOC by supporting North Atlantic Deep Water formation. This concept, taught as a textbook example in oceanography, linked shifts in the subtropical front position to variations in AMOC intensity. The AMOC is critical for regulating Earth’s climate, particularly in Europe and North America.
Sediment Core from the Agulhas Plateau
The research team analyzed a sediment core from International Ocean Discovery Program Site U1475, located 500 km south of South Africa on the Agulhas Plateau. They reconstructed north-south shifts of the Southern Ocean subtropical front using fossil dinocysts and organic lipid biomarkers. During the late Pliocene (3.6–2.6 million years ago), a warmer climate period, the front shifted south, opening a wider pathway for leakage, yet there was no corresponding strengthening of the AMOC. This contradicts the long-held belief that increased leakage directly boosts AMOC strength.
What's Next
The team plans to examine other glacial-interglacial transitions to further test the relationship between Agulhas Leakage and AMOC. It remains unclear how ongoing climate-driven changes in leakage will influence future AMOC stability.
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Nature Geoscience paper: Agulhas Leakage does not always strengthen AMOC
