Fig. 7

Horizontal distribution of vertical velocity w at a depth of 100 m averaged in a January–March, b April–June, c July–September, and d October–December during 1993–2016. Positive values show upward velocity. Contour intervals are \(1 {\times } 10^{-6}\,{\text {m\,s}}^{-1}\). Gray shadings indicate regions of no data because of small values of the Coriolis parameter and shallow water depth. Zonal and meridional thin solid lines denote locations of the w sections shown in Figs. 8b–e and 9b–e. Dotted square delineates the region where Nagano et al. (2016a) studied the QD variation in SST. In the solid square, vertical volume and temperature transports and SST tendency due to the vertical current variation were calculated as in Fig. 14