Projections for ocean currents’ transport and positioning from CMIP6 models

Abstract While climate change scenarios consistently project future changes in ocean circulation, an inter-basin assessment of the extent, intensity and underlying mechanisms driving these changes is still needed. Therefore, this study quantifies alterations in ocean currents’ volume transport (VT) and assess their relationship with subtropical gyre branch displacements and wind forcing changes based on projections from the Coupled Model Intercomparison Project Phase 6. To this end, monthly results from 24 models were analyzed considering a scenario where global warming of 2 $$^\\circ $$ C relative to the beginning of the century is extremely likely to be exceeded. In general, Northern Hemisphere western boundary currents exhibit an overall reduction in their VT by 2090–2100. In contrast, the Southern Hemisphere is projected to experience enhancements in the VT of the Brazil Current and East Australian Current, while the Agulhas Current is projected to undergo a decrease. The northern branches of the subtropical gyres generally shift northward, except for the Atlantic South Equatorial Current. Multiple linear regression and variance decomposition indicate that future VT changes are associated with basin-specific mechanisms. In the North Atlantic, Gulf Stream VT is jointly related to changes in the North Atlantic Current Drift position and wind stress curl anomalies. In the South Pacific, the East Australian Current changes are mostly related to South Pacific Equatorial Current migration, and in the Indian Ocean, Agulhas Current slowdown is primarily associated with wind stress curl anomalies. For the South Atlantic and North Pacific, the Brazil and Kuroshio Currents did not show significant relationships with the evaluated mechanisms.