Zanzibar Channel
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Figure 1: The Zanzibar Channel. It is located between the Tanzanian mainland and the island of Zanzibar. |
The larger geographical area within which the Zanzibar Channel lies is shown in Fig. 2 at the bottom of the page. The figure indicates that the dominant winds are those of the western Indian Ocean Monsoon, alternating between the Southwest Monsoon (which is actually southeasterly in the Zanzibar Channel) from May to October and the Northeast Monsoon from November to March (Hellerman and Rosenstein, 1983; Ngusaru and Mohammed, 2002). In contrast, for example, to the East Coast of North Africa, the East Coast of Africa has a narrower shelf. Small-scale processes in the Zanzibar Channel are therefore not isolated from large-scale processes beyond the shelf but instead influenced or even dominated by them (Shetye and Gouveia, 1998). One such large-scale process affecting the Zanzibar Channel is the northward flowing East African Coastal Current (EACC) (Swallow, 1991), which partly flows through the Zanzibar Channel with a speed varying from 0.25m/s to 2m/s (Newell, 1957). The EACC is the northern branch of the westward flowing South Equatorial Current. During the Southwest Monsoon the EACC is fast and merges into the northward flowing Somali Current while during the Northeast Monsoon the EACC is slow and merges with the southward flowing Somali Current into the Equatorial Counter Current. The EACC is primarily the western boundary current of the clockwise tropical gyre in the South Indian Ocean, which is driven by wind forcing over the open ocean.
