941 / 2024-09-19 21:00:54
Contribution of Agulhas Leakage to the “Saltier Atlantic-Fresher Indian” Trend
Agulhas Leakage; salinity trend; south Indian Ocean; south Atlantic Ocean
Session 60 - Indian Ocean Dynamics, Air-sea Interaction and Biogeochemical Cycles
Abstract Accepted
With the global warming, surface salinity increases (decreases) in evaporation (precipitation) dominated regions, the Atlantic–Indian salinity contrast increases, and the upper thermocline salinity maximum increases while the salinity minimum of intermediate waters decreases. The greater Agulhas system around southern Africa forms a key component of the global ocean circulation. This system feeds the upper arm of the Atlantic meridional overturning circulation (AMOC) through the leakage of warm, saline waters from the Indian Ocean to the Atlantic. Over longer periods, theory suggests its variability is associated with the large-scale wind field, in particular with the position of the maximum Southern Hemisphere westerly winds. These winds are related to the latitude of the oceanic subtropical front (STF), which separates the subtropical gyre from the Antarctic Circumpolar Current. In essence, if the westerlies shift southwards, as recent data suggest in a warming climate, then the oceanic ‘gateway’ between the African continent and the STF expands and leakage from the Indian Ocean to the Atlantic changes. Then the salt flux between the Atlantic and Indian Oceans changes. How does Agulhas leakage contribute to the “Saltier Atlantic-Fresher Indian” trend?