The influence of ENSO on the global oceans: a review of "the Atmospheric Bridge"

During El Niño/Southern Oscillation (ENSO) events, the enhanced precipitation over the anomalously warm water in the central and eastern Pacific affects the global atmospheric circulation. These atmospheric teleconnections 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, Atlantic, Indian and Southern Hemisphere Oceans. In addition, the developing SST anomalies in remote locations have the potential to feedback on the atmospheric circulation.

In this review, we will document the findings of previous papers and place them within the context of a recently completed set of 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 will discuss: i) the relationship between SST anomalies in the equatorial Pacific and those over the rest of the world's oceans; ii) how changes in the atmosphere associated with ENSO can force SST anomalies to form via surface energy fluxes, entrainment of subsurface waters into the surface mixed layer, and Ekman transports; iii) the influence of the atmospheric bridge on ocean conditions other than SSTs, including salinity and mixed layer depth (MLD); and iv) the extent to which SST anomalies generated by the atmospheric bridge feed back on the atmospheric circulation.