ABSTRACT
This chapter highlights the linkages between the observed changes in mid-latitude ocean circulation and wind-stress changes through shifts in atmospheric modes of variability. It focuses on the subtropical Western boundary currents (WBCs). In subtropical WBCs, the contrast between the warm waters that originate in the tropics and the cooler overlying air temperatures gives rise to complex air-sea interaction and local heat storage in unstratified water masses known as "mode waters." The Northern Hemisphere subtropical Atlantic and Pacific WBCs, the Gulf Stream (GS) and the Kuroshio Extension (KE), respectively, have been extensively studied. However, the dynamics of the GS are not as readily modeled as those of the KE as the GS circulation is embedded in the large-scale circulation known at the Atlantic Meridional Overturning Circulation. The two decades-long altimetry record has prompted examinations into longer time scale variability and possible trends related to climate change.
