Global Modes of Sea Surface Temperature Variability in Relation to Regional Climate Indices

A century-long EOF analysis of global sea surface temperature (SST) was carried out and the first six modes, independent by construction, were found to be associated with well-known regional climate phenomena: the El Nino-Southern Oscillation (ENSO), the Atlantic multidecadal oscillation (AMO), the Pacific decadal oscillation (PDO), the North Pacific Gyre Oscillation (NPGO), El Nino Modoki, and the Atlantic El Nino. Four of the six global modes are dominated by Pacific changes, the other two (M2 and M6) being associated with the AMO and Atlantic El Nino, respectively. The principal component time series of the ENSO (M1) and North Pacific (M3) modes are coherent at time scales >10 yr, and their interaction results in the traditional PDO pattern and the dominant mode of Pacific multidecadal variability. The M3 and PDO time series are well correlated, but the EOFs have different spatial patterns. The fourth mode (M4) has been strengthening since the 1950s and is related to the NPGO but also to El Nino Modoki, especially at the decadal scale. The fifth global mode (M5) is also spatially and temporally correlated to El Nino Modoki. The Pacific SST modes are further related to atmospheric forcing and the circulation of the North Pacific subpolar and subtropical gyres.