Decadal Variability in the Kuroshio–Oyashio Extension Simulated in an Eddy-Resolving OGCM

• DOI: 10.1175/jcli3793.1
• Publication Date: 2006-05-19T17:18:33Z
• Authors: Masami Nonaka; Hisashi Nakamura; Youichi Tanimoto; Takashi Kagimoto; Hideharu Sasaki
• Keywords: Subarctic climate; Forcing (mathematics); Extratropical cyclone; Hindcast

Abstract Through analysis of a hindcast integration an eddy-resolving quasi-global ocean general circulation model, decadal variability in the Kuroshio–Oyashio Extension region is investigated, with particular emphasis on that subarctic (Oyashio) and Kuroshio (KE) fronts. The KE front deep accompanied by sharp sea surface height (SSH) gradient modest temperature (SST) gradient. In contrast, shallow recognized as zone tight SST but not SSH. As decadal-scale change from warm period around 1970 to cool mid-1980s, those fronts model migrate southward observed, associated pronounced cooling confined mainly frontal zones. Reflecting distinctive vertical structure fronts, mixed layer strongest along front, whereas subsurface salinity changes are most front. Concomitantly their migration, two have undergone intensification. Associated reduced heat release into atmosphere, zones can be attributed neither direct atmospheric thermal forcing nor advective effect intensified KE, while intense Oyashio contribute zone. fact, time evolution found completely coherent, suggesting may governed different mechanisms. Decadal SSH seems largely explained propagation baroclinic Rossby waves forced anomalous Ekman pumping central North Pacific. This process alone cannot fully explain corresponding zone, where eastward propagating anomalies off Japanese coast seem superimposed wave signals.