1Role of Gulf Stream, Kuroshio-Oyashio and Their Extensions in Large-Scale Atmosphere-Ocean Interaction: A Review

Ocean-atmosphere interaction over the Northern Hemisphere western boundary current (WBC) regions, i.e. the Gulf Stream, Kuroshio-Oyashio, and their extensions, is reviewed with an emphasis on their role in basin-scale climate variability. SST anomalies exhibit considerable variance on interannual to decadal time scales in these regions. Low-frequency SST variability is primarily driven by basin-scale wind stress curl variability via oceanic Rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the WBC-related oceanic fronts. Rectification of the variability by meso-scale eddies, reemergence of the anomalies from the preceding winter, and tropical remote forcing also play important roles in driving and maintaining the low-frequency variability in these regions. In the Gulf Stream region, interaction with the deep western boundary current also likely influences the low-frequency variability. Surface heat fluxes damp the low-frequency SST anomalies over the WBC regions, thus heat fluxes originate with heat anomalies in the ocean and have the potential to drive the overlying atmospheric circulation. While recent observational studies demonstrate a local atmospheric boundary layer response to WBC changes, the latter’s influence on the large-scale atmospheric circulation is still unclear. Nevertheless, heat and moisture fluxes from the WBCs into the atmosphere influence the mean state of the atmospheric circulation, including anchoring of the latitude of the storm tracks to the WBCs