On the Difference in Strength between Atlantic and Pacific Undercurrents

Abstract

Abt. Reg. Ozeanogr., Inst. Meeresk., Univ. Kiel, Duesternbrooker Weg 20, D-2300 Kiel 1, FRG J (Journal-Article) M (Marine) From an earlier study of the longitudinal evolution of the equatorial zonal momentum balance in a nonlinear stratified simulation of the Atlantic equatorial undercurrent, it was shown that the annual mean simulated undercurrent reaches its maximum zonal velocity as it emerges from an accelerated deep inertial regime extending over about 15 degrees of longitude off the western boundary. Further east, frictional forces overcome the accelerating effect of the zonal pressure gradient force and the undercurrent keeps losing eastward momentum as it flows eastward. If the accelerating deep western regime extended over a wider range of longitudes the maximum emerging velocity would be larger. This is shown to occur in a nonlinear stratified simulation of the Pacific equatorial undercurrent because the western Pacific the...