Potential Predictability of Interannual Variability in the Kuroshio Extension Jet Speed in an Eddy-Resolving OGCM

Abstract

ariability in the Kuroshio Extension (KE) jet speed has been considered to impact the upper-ocean ecosystem. This study investigates potential predictability of interannual variability in the KE jet speed that could arise from the propagation time of wind-driven Rossby waves as suggested by previous studies, through prediction experiments with an eddy-resolving ocean general circulation model (OGCM) under the perfect-model assumption. Despite the small number of experiments available because of limited computational resources, the prediction experiments with no anomalous atmospheric forcing suggest some predictability for not only broad-scale sea surface height anomalies (SSHAs) but also the frontal-scale KE jet speed. The predictability is confirmed in a 60-yr hindcast OGCM integration as a significantly high correlation (r = 0.68) of 13-month running mean time series of the anomalous KE jet speed with SSHAs that appear in the central North Pacific Ocean 3 yr earlier. Although with fewer degrees of freedom, the same lag relationship can be found between satellite-measured SSHAs and the geostrophically derived KE jet speed.