In the western North Pacific from 0-35N 130-180E, the vertical and horizontal thermal structure of the baroclinic gyre systems in the region from 0-400 m depth has been mapped on a yearly basis from 1954-1974. From this measure of the baroclinic field of mass, the dynamic height (0/400 db) has been computed for each year, yielding geostrophic current indices of the major zonal currents....