Interannual variations of Kuroshio transport in the East China Sea and its relation to the Pacific Decadal Oscillation and mesoscale eddies

Abstract

AbstractResults of a data‐assimilative ocean model (JCOPE2) from 1993 to 2012 were used to examine the correlation between the Pacific Decadal Oscillation (PDO) index and interannual variations of the Kuroshio transport in the East China Sea (ECS) and the influences of mesoscale eddies on this correlation. In a period from 1993 to 2002, the Kuroshio transport estimated from the JCOPE2 reanalysis has a positive correlation with the PDO index. This well‐known correlation became weak or even disappeared when the analysis period was extended from 1993–2002 to 1993–2012. This occurs because the variation range of the PDO index became small during enhanced mesoscale eddy activity southeast of Taiwan in years after 2002. The eddies caused a larger variation in the Kuroshio transport in the years after 2002 than before 2002, and therefore, changed the correlation between the PDO index and Kuroshio transport in the ECS. The influence of mesoscale eddies on the Kuroshio transport has strong regional dependence: the Kuroshio transport from the area east of Taiwan to the midway along the shelf break in the East China Sea depends mainly on eddies arriving from southeast of Taiwan, while transport from the midway along the shelf break to the Tokara Strait depends mainly on the eddies arriving from northeast of Okinawa Island. The combination of PDO‐related signals and eddy‐related signals determines the interannual variations of the Kuroshio transport in the ECS and sufficient attention must be paid to the spatial dependence of the Kuroshio transport in the ECS on eddies.