Somali current

From Glossary of Meteorology

Somali Current

A prominent western boundary current in the northern Indian Ocean.

During the northeast monsoon season the Somali Current flows southward from 5° to 1°N in December, expanding to 10°N–4°S in January–February and contracting again to 4°N–1°S in March. It is then fed from the North Equatorial Current and discharges into the Equatorial Countercurrent. During all these months its speed is 0.7–1.0 m s-1. During the southwest monsoon the current develops into an intense northward jet with extreme surface speeds; 2 m s-1 have been reported for May and 3.5 m s-1 for June. The jet is fed from the South Equatorial Current and flows along the eastern coast of the Horn of Africa; part of it continues along the Arabian Peninsula as the East Arabian Current. South of 5°N the jet is shallow; southward flow continues below a depth of 150 m. North of 5°N the jet deepens and embraces the permanent thermocline. During its northward phase the Somali Current is associated with strong upwelling between 2° and 10°N. The upwelled cold water turns offshore near Ras Hafun (11°N), forming a large anticyclonic eddy with a diameter of about 500 km known as the Great Whirl. Eventually the water from the Somali Current enters the Southwest Monsoon Current.