Somali Current

The Somali Current can be found on the surface of the northern Indian Ocean, serving as a western boundary of this ocean. It is a movement of waters around the Indian Ocean, dispersing heat. Atmospheric circulation and ocean circulation together are the major mechanisms for global heat distribution. As atmospheric circulation defines large-scale air movements around the globe, ocean circulation refers to the patterned movement of particular waters.

In summer, a southwest monsoon blows upward from the east coast of the Horn of Africa. Carried along with the monsoon are the waters of the western Indian Ocean, moving in a northeast direction underneath, and powered by winds. These waters may reach speeds of 9 mi. per hour (14 km per hour). As the current reaches Somalia, the waters turn eastward. Some stay on near the Arabian Peninsula to form the East Arabian Current. Those that continue eastward eventually become the northeast monsoon during the autumn and winter, flowing southwest back to their origins. During the months of December and March, the Somali Current typically hovers between 5 degrees and 1 degree of latitude North of the equator, with this reach extending to span between 10 and 4 degrees latitude north during the central months of January and February.

The Somali Current is of interest because it creates an upwelling of cold water that is the only other region of such low surface temperatures within 10 degrees of the equator outside of Peru, and perhaps even colder. The cold surface temperatures around Peru are caused by the Peruvian or Humboldt Current, which is related to El Niño. The waters of the Somali Current swirl into what is known as the Great Whirl, an eddy with a diameter that can reach 500 km (approximately 311 mi.), spinning in an anticyclonic direction. Anticyclonic direction is opposite to the Earth’s rotation; in the Northern Hemisphere the eddy therefore spins clockwise. The upwelling occurs during the months of May through September, and can lower the surface temperature in the western Indian Ocean by up to 9 degrees F (5 degrees C). Ocean surface temperatures are an important data source for monitoring global warming; therefore, it is important to record the temperatures found during the northern (summer) swing of the Somali Current.

The Somali Current and other phenomena in the Indian Ocean were investigated at length in 1995 in a study that began in late 1994 and concluded in early 1996. It was an ambitious Project that attempted to record all data related to the Indian Ocean during that year, and was undertaken by the World Ocean Circulation Experiment (WOCE) Indian Ocean Expedition.