Estimating vertical velocity on the equator

Vertical velocity on the equator in the Central Pacific is estimated in four ways using mean CTD measurements assuming the following: 1) that the Equatorial Undercurrent core is a trajectory of flow; 2) that the flow is along isotherms; 3) that mass is conserved in the meridional-vertical plane; and 4) that mass is conserved three-dimensionally. It is remarkable that by using such simple and independent methods, all results agree so well, exhibiting an average vertical velocity at 90 m of 1.9 x 10 super(-3) cm s super(-1), with a standard deviation of only 0.3 x 10 super(-3) cm s super(-1). The results reported here demonstrate the ease with which reliable estimates of vertical velocity may be obtained on the equator, which may be useful in studies of the effects of upwelling on productivity and chemical nutrient renewal in the equatorial surface layer