Thermal structure and internal inertia oscillations after a typhoon passage in the East China Sea

Abstract

Four Autonomous Drifting Ocean Station (ADOS) drifters and two Acoustic Doppler current profilers (ADCPs) were deployed to observed thermal structure of the Kuroshio branch current in the East China Sea at the August in 2007. During the experiment a typhoon closely passed the study area and distinct typhoon signals are detected by the equipments. Just after the typhoon passage, sea surface temperature (SST) abruptly dropped down from 28°C to 24°C and thermocline, had exited between 30 – 50 m depth before the typhoon passage, disappear with the strong vertical disturbance. The inertia oscillation is detected in drifter trajectories after the typhoon passage during one week. In that period, the strong vertical shear of horizontal current component is analyzed in the drifters and ADCPs, even though the vertical temperature gradient is relatively mild. The vertical current shear is mainly induced by phase difference of clock-wise rotating inertia component. This internal inertia oscillation with weak vertical stratification can activate supplying of nutrients from the bottom layer to the euphotic zone and primary production in a shelf area. The vertical material transport and ecological processes after the typhoon passage in the East China Sea will be the future work.