Circulation in the Eastern Levantine Basin Determined by Inverse Methods

Abstract

A finite difference linear inverse model is applied to hydrographic data from six summer and fall cruises in a small area (250 × 200 km) of the eastern Mediterranean sea. The temperature and salinity equations are used to form a linear set of equations for the reference geostrophic velocities and the mixing coefficients, which are then solved by singular value decomposition. Advection by the horizontal velocities is the dominant process affecting the temperature and salinity fields in the region, and the model successfully resolves the horizontal velocities. Mixing and vertical advection are smaller by an order of magnitude, and the model cannot fully resolve the mixing coefficients and vertical velocities. The six velocity fields calculated from the data indicate a very strong variability that makes it difficult to identify a repeating summer or fall circulation patterns on the scale of the region covered by the data. An appendix contains the details of a new procedure for including linear inequalities in the solution of a rank deficient system of linear equations.