Welcome to the ASCLME Project

Between 2008 and 2013, the nine countries of the western Indian Ocean region, including Comoros, Kenya, Madagascar, Mauritius, Mozambique, Seychelles, Somalia, South Africa and Tanzania, will work together through the UNDP supported GEF financed Agulhas and Somali Current Large Marine Ecosystems (ASCLME) Project.


Somali Current system

Directly north of the Mozambique Channel, the northward setting current along the coast of the African continent is called the Zanzibar Current. It has as its main source the northern part of the westward flowing South Equatorial Current. During the north east monsoon season the Zanzibar Current is opposed by the southward flowing Somali Current and this meeting point usually shifts southward as the season progresses. It is only the surface expression of the Zanzibar Current that is prevented from moving northward; at depth the current continues as an undercurrent below the Somali Current. The north east monsoon occurs during the months of December to April, and is strongest in February. During the opposite wind phase, the south west monsoon season (June to October, maximum in August), the Zanzibar Current is strengthened considerably and forms the main tributary to the Somali Current which during this period carries water northward in an intense coastal jet. Speeds in this jet may reach very high values of up to 3.5 m/s. The southern part of the current is shallow. Further to the north it deepens.

The northward flow of the Somali Current during the south west monsoon season is not simply alongshore. The flow turns offshore at about 3°N. North of this point a strong upwelling cell has been observed to develop. The biological effect of this transitory upwelling cell has not been adequately studied. Two coastal gyres are then created at the sides of this upwelling cell. These gyres seem characteristic of the flow during the beginning of this season. As the season advances, these upwelling gyres shift northward, join together and by the time of the most intense part of the south west monsoon in August, the Somali Current is established as a continuous western boundary current from the Zanzibar Current in the south to the East Arabian Current in the north.

The monsoonal wind patterns vary somewhat from year to year and so will, in consequence, the seasonal development of the Somali Current. This inter-annual variability may have a decisive influence on the shelf circulation, on the marine ecosystem of the region and also on the success of the local fisheries. This variability has not been studied in a multi-disciplinary way. In general the coastal currents and the effect of offshore currents on the shelf area inshore of the Somali system have also been investigated in a very patchy and inadequate way. Long-term monitoring of currents, water masses and biota has been deficient.