Observed Linkages Between the Atmospheric Circulation and Oceanic‐Forced Sea‐Surface Temperature Variability in the Western North Pacific

Previous research suggests the extratropical atmospheric circulation responds to that sea‐surface temperature (SST) variability in the western North Pacific. However, the relative roles of oceanic and atmospheric processes in driving the SST anomalies that, in turn, seemingly influence the atmospheric circulation are unclear. Here, we exploit a simple stochastic climate model to subdivide the SST variability in the Kuroshio‐Oyashio Extension region into components forced by oceanic and atmospheric processes. We then probe the lead/lag relationships between the atmospheric circulation and both components of the SST variability. Importantly, only the oceanic‐forced SST variability is associated with robust atmospheric anomalies that lag the SSTs by 1 month. The results are consistent with the surface heat fluxes associated with atmospheric and oceanic‐forced components of the SST variability. Overall, the findings suggest that ocean dynamical processes in the western North Pacific play an important role in influencing the variability of the extratropical circulation. Plain Language Summary The study explores the role of midlatitude ocean dynamics in climate variability over the North Pacific sector. Previous studies suggest that the atmospheric circulation responds to sea‐surface temperature (SST) anomalies in midlatitude regions with strong oceanic currents, such as in the Kuroshio‐Oyashio Extension (KOE) region of the North Pacific. However, the role of heat transport by the ocean circulations in driving such SST anomalies and, in turn, the atmospheric response remains unclear. To address this outstanding issue, we use a simple model of midlatitude SST variability to isolate the oceanic and atmospheric‐driven components of SST variability in the KOE region. As in previous studies, an atmospheric circulation pattern is found to arise 1 month after SST anomalies in the KOE region during the winter season. Here it is shown that this pattern is strongly linked to the oceanic‐driven component of the SST anomalies, but not the atmospheric‐driven component. The findings thus provide novel evidence of the importance of midlatitude ocean dynamical processes for climate variability. Key Points Previous work shows that sea‐surface temperature (SST) anomalies in the western North Pacific precede extratropical circulation anomalies Here we explore the relative roles of oceanic and atmospheric‐forced SST anomalies in driving the lagged atmospheric response Only oceanic‐