FATES AND DYNAMICAL ROLES OF PINCH-OFF MESOSCALE EDDIES FROM THE KUROSHIO EXTENSION JET ANALYZED WITH THE ARMOR3D DIAGNOSIS

Abstract

 Mesoscale eddies are ubiquitous in the world ocean that frequently collide with currents and other eddies, leading to substantial alteration of the associated dynamics. To investigate fates and dynamical roles of pinch-off eddies from the Kuroshio Extension (KE) Jet, an eddy detection method was applied to ARMOR3D, a 3D global currents and density data set diagnosed from satellite and in-situ observations. Most of the detected pinch-off eddies are cyclonic on the south side of the KE region, while anticyclonic eddies are predominant on the north side. The former occurred 2.64 times as often as the latter, although in the entire North Pacific, cyclonic eddies occurred only 12.1% more frequently than anticyclonic eddies. We succeeded to determine pinch-off eddies recolliding with the Kuroshio by introducing a threshold distance between the Kuroshio path and terminal positions of eddies. Comparisons of the surface temperature and salinity before and after the eddy collisions clearly exhibit that the alteration of the Kuroshio path due to eddy collisions was quite influential in modifying the oceanic structures. It was also suggested that the stability of the Kuroshio path in the KE region is a key influencer on vigorous generation of such colliding pinch-off eddies.