Volume transport of the western boundary current penetrating into a marginal sea

Abstract

The amount of penetration of a western boundary current into a marginal sea which is connected to an open ocean by two narrow straits is estimated from a linear, steady and barotropic theoretical model. In this model the western boundary current in the open ocean is driven by a wind stress imposed at the sea surface. The inflow of the water of the open ocean into the marginal sea is caused by the pressure difference between two straits produced by the wind-driven circulation in the open ocean.

Main external parameters are combined into two non-dimensional parameters;$a = \mathop R\limits^{bD_0 }$ β and γ (the ratio of the depth of the marginal sea to that of the open ocean), whereb is the distance between north and south boundaries of the ocean,D ₀ is the depth of the open ocean, β is the latitudinal variation of the Coriolis parameter andR is the coefficient of friction. The friction is assumed to be proportional to the flow velocity.

In the limit of infinite α the volume transport into the marginal sea is not affected by the width of two straits and γ. It is mainly controlled by the wind stress and the positions of two straits. For finite values of α, however, the volume transport depends considerably on γ and the width of the straits.

Guided by both this model and physical considerations, we obtained a relation between the volume transport into the marginal sea and the external parameters. This relation predicts that about 2 % of the volume transport of the Kuroshio penetrates into the Japan Sea.