80–90-Year Principal Oscillation Pattern in ERSSTv5 Global SSTs

Abstract A modified principal oscillation pattern (POP) analysis has been formulated to identify the POP in the Extended Reconstructed SST, version 5 (ERSSTv5), dataset with both the radiative forcing trend and the effect arising from year-to-year variability removed from the decadal running means. The first POP, with a period of 84 years and e -folding time of 340 years, longer than the oscillation period, explains 25% of the SST multidecadal variability. The real and the imaginary parts of the eigenvector of the POP relate to multidecadal variability in the Atlantic multidecadal oscillation (AMO) and the Antarctic Circumpolar Current (ACC), respectively. Multidecadal variability in the Atlantic and Pacific Oceans is shown to be related to the real part, while the imaginary part influences the Southern Hemisphere oceans. The evolution of the POP cycle is described in terms of the interaction between the AMO and the ACC and is consistent with the variability of the independently reconstructed sea level pressure dataset HadSLP2. Similar results are found for the SST datasets JMA Centennial Observation-Based Estimates, version 2 (COBE2), ERSSTv3b, and HadISST1.1 which all have damped oscillation periods in the range 80–90 years and large e -folding times greater than their periods. Significance Statement This is the first study of an 80–90-yr damped oscillation in observed global sea surface temperature with the radiative forcing trend and the effect arising from year-to-year variability removed. This multidecadal oscillation involves an interaction between the Atlantic multidecadal oscillation and the Antarctic Circumpolar Current over the oscillation period. The proposed methodology can be used to evaluate climate models in their ability to simulate the observed decadal variability in sea surface temperature.