Localization of Multidecadal Variability. Part I: Cross-Equatorial Transport and Interbasin Exchange

Multidecadal SST variability is studied in idealized one- and two-ocean-basin configurations, using simulations with the Modular Ocean Model. The authors demonstrate that the multidecadal variability on the global “conveyor type” circulation is localized in the North Atlantic Ocean. Interbasin exchange processes determine the locations where regions of deep-water formation occur and induce a localization of SST multidecadal anomalies in the Atlantic. The physics of this localization is subsequently investigated by considering more equatorially symmetric background flows in two-basin and one-basin configurations. A cross-equatorial flow in the Atlantic induces the localization of the multidecadal variability in the North Atlantic. By using the mechanism of multidecadal variability as proposed in 2002 by Te Raa and Dijkstra in a single-hemispheric configuration, the physics of these localization processes can be explained.