Mechanisms of reemergence in the central North Pacific revealed by a mixed layer heat budget analysis

Wintertime sea surface temperature (SST) anomalies that disappear in summer and recur in the following winter is known as “reemergence”. Mechanisms of reemergence in the North Pacific are investigated quantitatively for the first time by conducting an online mixed layer heat budget analysis with a realistic ocean model simulation. In contrast to past studies that have emphasized the importance of vertical entrainment of subsurface temperature anomalies, it is shown that several mechanisms are operating in “reemergence”. In particular, anomalous Ekman meridional advection of the mean meridional temperature gradient induced by zonal wind stress anomalies plays an important role in many years. Also, coincidence in the sign of SST anomalies in winter and surface heat flux anomalies in the following autumn leads to recurrence of SST anomalies.