On the seasonal variation in in- and outflow volume transport of the Japan Sea

Abstract

Dynamics of the seasonal variation in the volume transport of the Tsushima Current is considered from the view point that the in- and outflow of the Japan Sea is essentially due to the sea level difference between the inflow region and outflow region. The sea level difference is estimated by a numerical model driven by the observed wind stress over the North Pacific. It is shown that the sea level difference is largest in winter and relatively small in summer to autumn. On the other hand, because the density stratification is very weak in winter, water has a tendency to flow along the geostrophic contour. This decreases the in- and outflow transport. The transport of the in- and outflow of the Japan Sea varies with the intensity of density stratification rather than to the sea level difference, though its mean essentially depends on the sea level difference. The observed maximum (minimum) inflow transport in summer (winter) is due to the strong (weak) density stratification in the straits. The low density river water discharged in the East China Sea plays an important role in the larger inflow of the Tsushima Current in summer to autumn.