Interannual Variability of Sea Surface Temperature in the Southwest Pacific and the Role of Ocean Dynamics

This paper investigates the mechanisms causing interannual variability of upper ocean heat content and sea surface temperature (SST) in the southwest Pacific. Using the ECCOv4 ocean reanalysis it is shown that air-sea heat flux and ocean heat transport convergence due to ocean dynamics both contribute to the variability of upper ocean temperatures around New Zealand. The ocean dynamics responsible for the ocean heat transport convergence are investigated. It is shown that SSTs are significantly correlated with the arrival of barotropic Rossby waves estimated from the South Pacific wind stress over the latitudes of New Zealand. Both Argo observations and the ECCOv4 reanalysis show deep isotherms fluctuate coherently around the country. The authors suggest that the depth of the thermocline around New Zealand adjusts to changes in the South Pacific winds, modifies the vertical advection of heat into the upper ocean, and contributes to the interannual variability of SST in the region.