Figure 3

(a) Model bottom topography around the study region. The green and blue rectangles indicate the region where the sea-surface chlorophyll-a and the longitude of the OBTWC path are estimated in Fig. 4b. Contours of 200 m depth are denoted by white contours. (b) Model time series of northwestward salt transport with reference salinity of 34.0 (Q_S; kg s⁻¹) across the gray line of (a) (black bars) and relative vorticity averaged over the blue rectangle of (a) (blue lines) during April–May. Model composite average of the sea-surface velocity vectors greater than 0.05 m s⁻¹ (arrows) and sea-surface salinity lower than 33.9 (color) when Q_S ≤  − 7.0 × 104 kg s⁻¹ (c) and − 0.9 × 104 kg s⁻¹ ≤ Q_S ≤  − 0.7 × 104 kg s⁻¹ (d). Contours of 200 m, 400 m, 1000 m, and 2000 m depths are presented respectively as red, purple, green, and blue contours. The dashed line and rectangle are the same as the gray line and blue rectangle of (a). IDL 9.0 (https://www.nv5geospatialsoftware.com/Products/IDL) is used in generating the bathymetry based on the 1-km JTOPO30 data set provided by the Marine Information Research Center of the Japan Hydrographic Association (www.mirc.jha.or.jp/products/JTOPO30v2/).