A method for the determination of absolute geostrophic velocities in the sea

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Abstract
A method utilizing hydrographic data and vertically-averaged currents for the determination of absolute geostrophic velocities in the sea is described. Relative dynamic depths are interpolated on a selected grid of points by (i) using the linear least-squares estimation for a given function with “unknown data” and (ii) solving the Poisson equation with Dirichlet boundary conditions and a finite number of linear constraints within the domain investigated. Once the fields of relative velocities are computed and the measured vertically-averaged currents are interpolated on the grid using the same procedure as for the relative dynamic depths, the absolute currents may be calculated by simply subtracting the vertically-averaged relative velocities from the vertical averages of the currents. This method is illustrated by an example from the Rijeka Bay, a small basin in the northeast Adriatic Sea. The results for the Rijeka Bay are interesting from a qualitative point of view, whereas for the exact quantitative reproduction of the Bay circulation, higher-order dynamics should be invoked. It is concluded that the method in its original form is more suitable for the open sea, and the experiment needed for its application in such an environment is briefly described. DOI: 10.1111/j.1600-0870.1987.tb00291.x