Monitoring Ocean-atmosphere Interactions in Western Boundary Current Extensions

Western boundary currents as they extend eastward into the ocean basin (referred to here as WBCEs) are regions of intense air-sea interaction, where the ocean loses heat and moisture to the atmosphere and absorbs carbon dioxide. Air-sea interactions in WBCEs can affect weather and climate both locally and remotely, on time scales of days to decades. Thus significant societal benefit can be achieved by improving their representation in numerical models of the atmosphere and ocean. To this end, WBCE data are needed for assimilation into numerical models, for assessment of model realism, and for analyses of climate processes. WBCE include the Kuroshio Extension in the North Pacific, the Gulf Stream in the North Atlantic, the Agulhas Return Current in the South Indian Ocean, the East Australian Current in the South Pacific, and the Brazil-Malvinas Confluence in the South Atlantic. The open-ocean strong currents, sharp fronts, and energetic synoptic variability make WBCEs challenging regions to observe, but existing technology will allow comprehensive sustained observations of these important regions. While our primary focus is on monitoring ocean-atmosphere interactions and ocean ventilation related to heat and freshwater exchanges, these depend upon the location of the current, depth of temperature anomalies (heat content), and the threedimensional circulation, features that also can affect the distribution of biogeochemical properties. The observing system strategy developed here thus attempts to provide a coordinated system that would act as a framework for multidisciplinary observations.