The Somali Current in autumn 1984, before the onset of the north-east monsoon

Abstract

The Somali Current undergoes vigorous variations during the course of the south-west monsoon. Although the initial phases of this response were fairly intensively studied during the FGGE Indian Ocean Experiment (INDEX) in 1979^1,2, relatively little is known about what happens in the late summer monsoon and the transition to the winter monsoon. In October 1984, we carried out measurements in the Somali Current regime with a shipboard acoustic Doppler current profiler which showed that a continuous Somali Current did not exist at this time: instead, the cross-equatorial flow with a transport of 12 × l0⁶ m³ s⁻¹ in the upper 100 m identified by relatively low surface salinities, was found to turn offshore south of 2° N. Between 6 and 11° N, a large closed anticyclonic gyre, marked by relatively high surface salinities, was found with a transport of 32 × 10⁶ m³ s⁻¹ in the upper 250 m, which is significantly greater than previously estimated from geostrophic calculations.