Analogous seasonal evolution of the South Atlantic SST dipole indices

• Published in: Atmospheric Science Letters
• Main Authors: Nnamchi, Hyacinth C., Kucharski, Fred, Keenlyside, Noel S., Farneti, Riccardo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Austral; South Atlantic Ocean
• Online Access: https://oceanrep.geomar.de/id/eprint/40056/; https://oceanrep.geomar.de/id/eprint/40056/1/asl2781.pdf; https://oceanrep.geomar.de/id/eprint/40056/2/asl2781-sup-0001-AppendixS1.docx; https://doi.org/10.1002/asl.781

Two variants of sea-surface temperature (SST) dipole indices for the South Atlantic Ocean (SAO) has been previously described representing: (1) the South Atlantic subtropical dipole (SASD) supposedly peaking in austral summer and (2) the SAO dipole (SAOD) in winter. In this study, we present the analysis of observational data sets (1985–2014) showing the SASD and SAOD as largely constituting the same mode of ocean–atmosphere interaction reminiscent of the SAOD structure peaking in winter. Indeed, winter is the only season in which the inverse correlation between the northern and southern poles of both indices is statistically significant. The observed SASD and SAOD indices exhibit robust correlations (P ≤ 0.001) in all seasons and these are reproduced by 54 of the 63 different models of the Coupled Models Intercomparison Project analysed. Their robust correlations notwithstanding the SASD and SAOD indices appear to better capture different aspects of SAO climate variability and teleconnections