Direct Observations of North Pacific Subsurface Low Potential Vorticity Water Impinging on the Kuroshio

Abstract

In this study, for the first time, we found a Subsurface Low Potential Vorticity Water (SLPVW) to the east of Taiwan Island (122$\mathit{°}$–124$°\text{E}$, 21.67$\mathit{°}$–23$\mathit{°}\text{N}$) via an array comprising 12 current and pressure-recording inverted echo sounders (CPIESs) from 25 June 2018 to 29 July 2019. This SLPVW exhibits remarkable intraseasonal variability, with an ∼100-day period east of Taiwan Island, corresponding with the variability in mesoscale eddies. Compared with large-scale climatological mean circulation, mesoscale eddy can trap SLPVW as a highway westward transport. In addition, the SLPVW impingement results in a significant subsurface velocity variation (about 10 cm/s) in the 200–400 m layer. These findings shed new light on the mechanisms of the intraseasonal variation in the Kuroshio subsurface layer.