Role of Reemergence in the Central North Pacific Revealed by a Mixed Layer Heat Budget Analysis
Kazumichi Murata, Shoichiro Kido, Tomoki Tozuka
Abstract
Abstract Wintertime sea surface temperature (SST) anomalies that disappear in summer and recur in the following winter are known as “reemergence.” The role of reemergence in recurrent SST anomalies in an area in the central North Pacific is 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 recurrence of SST anomalies during 1977–1999. 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.