Relationship between sea surface temperature anomalies in the Southwestern Atlantic Continental Shelf and atmospheric variability on intraseasonal timescales

Abstract

The intraseasonal (IS) variability of the sea surface temperature (SST) in the Southwestern Atlantic Northern Argentinean Continental Shelf (SWACS NACS, 45-33°S -70-50°W), and its relationship with that in the atmosphere, was studied for the austral warm season. SST satellite data (11-km resolution NOAA CoastWatch Program) and data of different atmospheric variables (Reanalysis1 NCEP/NCAR and ERA-Interim) were used. Data were ltered using a 10-90day lter to isolate the IS variability. A Principal Component analysis was applied then to the ltered SST anomalies (SSTA) and the activity of the leading modes was described through the corresponding temporal series. The rst three modes are signi cant. EOF1 (25.7% of variance) exhibits SSTA of opposite sign to the north/south of 42°S. EOF2 (9.0%) and EOF3 (5.1%) are related with centers of SSTA of opposite sign located off the Uruguayan coast and in the middle shelf. Composites of SSTA and of key atmospheric variables were made considering the days in which the main modes were active. They show that the SSTA described by the three modes are associated with distinctive regional sea level pressure anomalies that, in turn, seem to be related to atmospheric Rossby wave trains extending from the Australia area towards South America. The corresponding atmospheric wave sources vary depending on the mode. These results show, therefore, that the SSTA in the SWACS NACS exhibit signi cant IS variability that is, in part, locally and remotely in uenced by atmospheric anomalies oscillating on similar timescales. These ocean-atmosphere teleconnections could help to improve ocean predictability at those timescales in the future.