Extratropical Air-Sea Interaction During ENSO: Atmospheric Forcing and Oceanic Feedbacks (Invited)

Atmospheric teleconnections associated with El Niño/Southern Oscillation (ENSO) alter the near-surface temperature, humidity and wind, and the distribution of clouds, which in turn, can influence the ocean far from the equatorial Pacific. Thus, the atmosphere can act as a "bridge" between SST anomalies in the equatorial Pacific and ocean conditions in the North Pacific and other ocean basins. The atmospheric bridge is examined using observations and a recently completed set of 16 atmospheric GCM simulations where observed SST anomalies for the period 1950-2000 are specified in the tropical Pacific, while the remainder of the global ocean is represented by a grid of mixed layer ocean models. We examine the relationship between SST anomalies in the equatorial Pacific and those over the Northern Hemisphere oceans, and how changes in the atmosphere associated with ENSO can create SST anomalies via surface energy fluxes, entrainment of subsurface waters into the surface mixed layer, and Ekman transports. Of particular interest is the new finding that large SST anomalies develop in the western North Pacific during the summer when ENSO is just beginning.