Remote impacts of the 18.6 year period modulation of localized tidal mixing in the North Pacific

Abstract

The impact of the 18.6 year period modulation of the localized strong tidal mixing on the annual mean sea surface temperature (SST) in the open North Pacific Ocean is analyzed in a numerical experiment using an ocean general circulation model. Oscillatory SST anomalies induced in this model move eastward along the boundary between the subarctic and the subtropical gyres from the western boundary to the central Pacific in about 10 years, with a speed slower than that of the surface currents. Anomalous currents in the upper 300 m play an important role in inducing SST anomalies. These anomalous currents are coupled to subsurface density anomalies and could be related to eastward moving, low-mode (second or higher), baroclinic long Rossby waves. These results suggest that the 18.6 year modulation of localized strong tidal mixing can influence large-scale SST and/or heat flux, and thus climate, as a result of remote impacts associated with changes in the mid-depth density structure, induced locally where mixing is strong, that move horizontally into the open ocean. Key Points The 18.6-year periods tidal cycle could influence large-scale SST. Changes in mid-depth density could link tidal mixing to decadal climate. East-ward moving low-mode long Rossby wave may play an important role. ©2013. American Geophysical Union. All Rights Reserved.