Tidal currents and Kuroshio transport variations in the Tokara Strait estimated from ferryboat ADCP data

Abstract

From 2003 to 2011, current surveys, using an acoustic Doppler current profiler (ADCP) mounted on the Ferry Naminoue, were conducted across the Tokara Strait (TkS). Resulting velocity sections (1234) were used to estimate major tidal current constituents in the TkS. The semidiurnal M2 tidal current (maximum amplitude 27 cm s−1) was dominant among all the tidal constituents, and the diurnal K1 tidal current (maximum amplitude 21 cm s−1) was the largest among all the diurnal tidal constituents. Over the section, the ratios, relative to M2, of averaged amplitudes of M2, S2, N2, K2, K1, O1, P1, and Q1 tidal currents were 1.00:0.44:0.21:0.12:0.56:0.33:0.14:0.10. Tidal currents estimated from the ship‐mounted ADCP data were in good agreement with those from the mooring ADCP data. Their root‐mean‐square difference for the M2 tidal current amplitude was 2.0 cm s−1. After removing the tidal currents, the annual‐mean of the net volume transport (NVT) through the TkS ± its standard derivation was 23.03 ± 3.31 Sv (Sv = 106 m3 s−1). The maximum (minimum) monthly mean NVT occurred in July (November) with 24.60 (21.47) Sv. NVT values from the ship‐mounted ADCP were in good agreement with previous geostrophic volume transports calculated from conductivity temperature depth data, but the former showed much finer temporal structure than those from the geostrophic calculation.

Tidal and residual currents across the northern Ryukyu Island chain observed by ferryboat ADCP

“…Although we did not compare our tidal currents with other observational data, the harmonic analysis method we used to eliminate the tidal currents has been successfully adopted by Zhu et al . []; moreover, their semidiurnal and diurnal tidal ellipses agreed very well with moored ADCP data at two stations.…”

“…Detailed information for the ferry schedule and the procedure for reducing the estimated uncertainty in the ADCP data can be found in Zhu et al . []. With this ADCP data set, Zhu et al .…”

“…With this ADCP data set, Zhu et al . [] successfully estimated major tidal current constituents in the Tokara Strait.…”

Phytoplankton growth and consumption by microzooplankton stimulated by turbulent nitrate flux suggest rapid trophic transfer in the oligotrophic Kuroshio

“…DL: below the detection limit. Zhu et al, 2017) passed through the Tokara Strait (150 km), then the phytoplankton in a 10 m thick layer could have consumed nitrate equivalent to a nitrate enrichment of 0.41 µmol L −1 . The EXP b experiment was conducted using triplicate 1.2 L polycarbonate bottles with microzooplankton as grazers and involved dilutions of the microzooplankton standing stocks in the original water samples so that the concentrations of microzooplankton equaled 1, 0.6, 0.3, or 0.1 times the concentration in the undiluted water.…”

Tempo‐Spatial Variations of the Kuroshio Current in the Tokara Strait Based on Long‐Term Ferryboat ADCP Data

“…From January 2003 to March 2012, Kagoshima University conducted full‐depth acoustic Doppler current profiler (ADCP) measurements across the Tokara Strait, using the round‐trip ferryboat Naminoue between Kagoshima and Okinawa (Liu et al, ; Zhu et al, ). The repeated full‐depth ferryboat ADCP surveys provide unprecedented temporal and spatial resolution to resolve the variation in the Kuroshio across the Tokara Strait.…”