Abstract
Variation of sea surface temperature (SST) results from a host of mechanisms involving both the ocean and atmosphere. The atmospheric forcing on SST is usually hypothesized as white noise to reflect the transient and chaotic nature of the atmosphere in contrast to the large heat inertial of the ocean mixed layer. This study presents evidence that the non-white-noise memory of atmospheric forcing has a substantial contribution to SST variability. According to the computed decorrelation time scale, atmospheric forcing can persist for two to five months in the extratropical North Pacific and North Atlantic. Without considering this atmospheric memory, white noise atmospheric forcing underestimates the observed extratropical SST variance by more than 50%; whereas an atmospheric forcing with observed memory produces an SST variability comparable to observations. Approximately 70% of the extratropical atmospheric memory evidently originates from the tropical oceans, including the Niño3.4 region and the tropical North Atlantic, highlighting the significance of tropical-extratropical teleconnection in maintaining the observed SSTA variability in the extratropics.