Assessment of responses of North Atlantic winter sea surface temperature to the North Atlantic Oscillation on an interannual scale in 13 CMIP5 models

Abstract

This study evaluates the response of winter-average sea surface temperature (SST) to the winter North Atlantic Oscillation (NAO) simulated by 13 Coupled Model Intercomparison Project Phase 5 (CMIP5) Earth system models in the North Atlantic (NA) (0–65∘ N) on an interannual scale. Most of the models can reproduce an observed tripolar pattern of the response of the SST anomalies to the NAO on an interannual scale. The model bias is mainly reflected in the locations of the negative-response centers in the subpolar NA (45–65∘ N), which is mainly caused by the bias of the response of the SST anomalies to the NAO-driven turbulent heat flux (THF) anomalies. Although the influence of the sensible heat flux (SHF) on the SST is similar to that of the latent heat flux (LHF), it seems that the SHF may play a larger role in the response of the SST to the NAO, and the weak negative response of the SST anomalies to the NAO-driven LHF anomalies is mainly caused by the overestimated oceanic role in the interaction of the LHF and SST. Besides the THF, some other factors which may impact the relationship of the NAO and SST are discussed. The relationship of the NAO and SST is basically not affected by the heat meridional advection transports on an interannual timescale, but it may be influenced by the cutoffs of data filtering, the initial fields, and external-forcing data in some individual models, and in the tropical NA it can also be affected by the different definitions of the NAO indices.