Exchange fluxes between the Ria de Vigo and the shelf: a bidirectional flow forced by remote wind

In the Ría de Vigo (western coast of the Iberian Peninsula) the seasonal pattern associated with shelf winds at these latitudes produces upwelling/downwelling episodes that affect the residual circulation. The aim of this paper is to go deeply into the interaction between remote winds and the dynamics of the ria aided by an inverse model. In the Galician r ias the box models (inverse models) have been developed from a two-dimensional (2-D) point of view since the classical baroclinic residual circulation in positive estuaries has a vertical distribution (freshwater outflow through the surface layer and inflow through the bottom layer). However, recent work in the Ría de Vigo has shown the existence of a 3-D residual circulation in the seaward region of the ria. During upwelling (downwelling) conditions a coastal jet enters (leaves) the ria through the northern mouth and leaves (enters) through the southern mouth. The inverse model developed in this paper is a 3-D kinematic box model based on tracer and volume balances with the constraint of nonnegative vertical exchange coefficients. The fluxes obtained confirm, during some periods, the 3-D residual circulation overlying the classical 2-D scheme. It is shown how the 3-D pattern affects the inner ria, causing transversal differences in the flow field. In addition, the model results have been helpful in the discussion of a possible barotropic bidirectional flow associated with remote winds. The results have set the basis for the existence of a bidirectional flow originated by a barotropic interaction with the shelf upwelling.