Winter monsoon circulation of the northern Arabian Sea and Somali Current

The winter monsoon circulation in the northern inflow region of the Somali Current is discussed on the basis of an array of moored acoustic Doppler cu rrent profiler and current meter stations deployed during 1995-1996 and a s hip survey carried out in January 1998. It is found that the westward inflo w into the Somali Current regime occurs essentially south of 11 degrees N a nd that this inflow bifurcates at the Somali coast, with the southward bran ch supplying the equatorward Somali Current and the northward one returning into the northwestern Arabian Sea. This northward branch partially supplie s a shallow outflow through the Socotra Passage between the African contine nt and the banks of Socotra and partially feeds into eastward recirculation directly along the southern slopes of Socotra. Underneath this shallow sur face flow, southwestward undercurrent flows are observed. Undercurrent infl ow from the Gulf of Aden through the Socotra Passage occurs between 100 and 1000 m, with its current core at 700-800 m, and is clearly marked by the R ed Sea Water (RSW) salinity maximum. The observations suggest that the maxi mum RSW inflow out of the Gulf of Aden occurs during the winter monsoon sea son and uses the Socotra Passage as its main route into the Indian Ocean. W estward undercurrent inflow into the Somali Current regime is also observed south of Socotra, but this flow lacks the RSW salinity maximum. Off the Ar abian peninsula, eastward boundary flow is observed in the upper 800 m with a compensating westward flow to the south. The observed circulation patter n is qualitatively compared with recent high-resolution numerical model stu dies and is found to be in basic agreement.