Coherent interannual and decadal variations in the atmosphere-ocean system

Abstract

We investigate the source of poleward propagating atmospheric zonal wind anomalies, originating at the equator and penetrating to high latitudes in both hemispheres in conjunction with ENSO [Dickey et al., 1992], and report the discovery of similar variability on decadal and longer timescales. Since atmospheric dissipation times are generally on the order of a month or less, we examine the ocean as a "memory" source for these globally coherent anomalies. This hypothesis is substantiated by the observation of complementary oscillation in the sea surface temperature (SST) field; further, we detect a robust decadal variability (∼10-12 yrs) in both the SST and contemporaneous atmospheric angular momentum (AAM) series. Analyzing GISST SST data beginning in 1902, we confirm this decadal mode and find signatures of longer (multidecadal) SST variability centered in the equatorial and North Pacific.