Indian Monsoon Current

The northern Indian Ocean follows a seasonal rhythm that mariners have recognised for nearly a thousand years. Winter winds drive an upper-ocean flow westward from the Bay of Bengal, around India and Sri Lanka and across the Arabian Sea. In summer the circulation reverses, carrying water eastward from the African side toward Bengal.

The Somali Current participates in the same seasonal change near the Horn of Africa. A voyage therefore depended on its place in the year as well as on the distance between ports. The continental landmass north of the ocean helps create this pattern: land heats and cools more quickly than the sea, altering pressure and the direction of prevailing winds.

This distinguishes the region from the more persistent tropical trade winds of the Atlantic and Pacific. Before later measurements, practical knowledge came through repeated navigation in waters whose drift could favour one direction in one season and oppose it in another. The current formed part of the environmental knowledge required for sustained travel across the Indian Ocean.