Convergence in the equatorial surface jets of the Indian Ocean

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Abstract
Twenty‐one surface drifters have been deployed in the equatorial Indian Ocean since 1979. Their trajectories are used to estimate the near‐surface meridional convergence in eastward surface jets, which is found to be typically of the order of −0.8×10−6 s−1. A 2.5‐year time series of currents and temperature profiles not made simultaneously, but in the same area, at Gan (73°E, 0°30′S; Knox (1976)), is also analyzed. The balance of forces averaged vertically in the mixed layer is consistent with a horizontal convergence of the order of −0.3×10−6 s−1, when the surface currents are eastward. The difference between the surface estimate based on the buoy trajectories and the other estimate is consistent with the expectation that convergence should be maximum near the surface. Zonal velocities are also larger near the surface, with a mean vertical shear of 0.4×10−2 s−1 when mixed layers are deeper than 60 m.