The Dominant Mode of Southern Ocean Sea Surface Temperature and its Relationship with the Southern Annular Mode

The variability in Southern Ocean (SO) sea surface temperature (SST) has drawn increased attention due to its unique physical features. Spatial and temporal characteristics of SO SST anomalies (SSTA) are addressed on both monthly and seasonal scales in this study. The dominant mode of SO SSTA is referred to as the Southern Ocean Dipole (SOD), and it represents a hemispheric-wide oscillation of SSTA between the middle and high latitudes. The positive (negative) phase of the SOD reflects warmer (colder) SSTA in the middle latitudes, whereas colder (warmer) SSTA in the high latitudes. The SOD features strong zonal symmetry, and could reflect more than 50% of total zonal-mean SSTA variability. The primary variability of the large-scale SO SSTA meridional gradient is determined by SOD activity, and positive (negative) phase of the SOD corresponds to stronger (weaker) Subantarctic and Antarctic Polar fronts. In general, the influence of the SAM on the SOD is mainly through perturbations of local surface wind, while the meridional transport of SSTA may also plays an important role in the influence of the ENSO on the SOD.