Computation of Upwelling and Sinking from Direct Measurements of Horizontal Currents

Abstract

By a transformation of hydrodynamical equations of viscous liquid, expressions were derived, by which both the speed of upwelling and sinking, and the vertical profile of the coefficient of vertical eddy viscosity can be computed at the same time. For numerical computation, data of pressure gradients and of the velocity components of horizontal currents and their horizontal derivatives are necessary. As data satisfying this requirements direct current measurements carried out with Roberts meters in the Swan Song Expedition 1961 in the Eastern Tropical Pacific are available. Resulting coefficient of vertical eddy viscosity which must be positive by nature, very often has negative sign, probably, due to vanishing of the denominator in the solution of simultaneous equations and consequent predomination of errors from various other sources.
As possible sources of these errors, mention was made of the inadequateness of the accuracy in current measurement, the possibility of large fluctuations of ocean currents at or close to the Equator and the fact that the ocean current measurements and the hydrographic observations for evaluating mass distribution in the area were not made simultaneously.