Role of Kuroshio frontal eddy in exchange between shelf water and Kuroshio water in East China Sea

Basic patterns of the reversal of the Kuroshio water toward the shelf,intrusion of the shelf mixed waterinto the Kuroshio and uplifting of the near-bottom nutrient-rich water into the upper layer by the pumping of the frontal eddy are analyzed on the basis of satellite infrared images and hydrologic,chemical and biological observations.Results show that the Kuroshio frontal eddies play a very important role in the exchange between the shelf water and the Kuroshio water.The estimation of the average volume transports for three frontal eddy events indicates that the shelf mixed water entrained by an eddy into Kuroshio is 0.44×10⁶ m³/s and the reversal Kuroshio water onto the shelf region only 0.04×10⁶ m³/s.Along the whole shelf edge,the volume transport of the shelf mixed water entrained by the eddies into the Kuroshio is 1.8×10⁶ m³/s.The nutrient (NO₃-N) flux pumped to the euphotic zone and input to the continental shelf through a column with 1 m wide is 974 μmol/(s·m) when there is frontal eddy and only 79 μmol/(s·m) in the case of no frontal eddy.Yearly nutrient (NO₃-N) flux input to the shelf area caused by the frontal eddy is 1.7×10⁶ t/a.