On the Contrast between the Seasonal Cycles of the Equatorial Atlantic and Pacific Oceans

Abstract

Although the winds on the equator at 28°W in the Atlantic and 140°W in the Pacific have similar seasonal variations, the current fluctuations have pronounced differences. In the Pacific the maximum speed of the Equatorial Undercurrent, attained in the northern spring, can exceed 140 cm s?1, while the minimum speed, in the autumn, is less than 80 cm s?1. In the Atlantic the maximum speed of 80 cm s?1 hardly varies seasonally, although it tends to be largest in the autumn. Analyses of results from a realistic simulation of the equatorial currents indicate that the larger zonal extent of the Pacific, and the seasonal variations of the winds over the western Pacific, which can be out of phase with those in the east, are the principal reasons for the differences between the Atlantic and Pacific.