The Somali Current, located off the coast of East Africa, is an ocean current with highly unusual behavior. Its uniqueness stems from dramatic seasonal changes that shape both its flow and the marine environment it influences.
Location and General Characteristics
The Somali Current flows along the coastlines of Somalia and Oman in the western Indian Ocean. It is a Western Boundary Current, a classification it shares with prominent currents like the Gulf Stream in the Atlantic Ocean. However, its behavior deviates significantly from these more stable counterparts. The current is relatively shallow, particularly south of 5°N, and responds rapidly to external forces.
The Monsoon Connection
The Somali Current’s unusual nature is intrinsically linked to the powerful Indian Ocean monsoons. These monsoons involve a complete seasonal reversal of wind patterns over the region. During the Northern Hemisphere’s summer, the Southwest Monsoon brings strong winds blowing northeastward along the East African coast. Conversely, the Northeast Monsoon in winter sees winds shift to blow southwestward.
The powerful, low-level atmospheric jet known as the Findlater Jet, or Somali Jet, develops during the Southwest Monsoon, blowing parallel to the coasts of Somalia and Oman. This intense wind stress directly transfers energy to the ocean, causing the current to respond rapidly.
Seasonal Reversal and Extreme Strength
The Somali Current exhibits a complete seasonal reversal in its flow. During the Southwest Monsoon (June to September), the current flows northeastward along the coast, reaching exceptional speeds. Velocities can reach up to 3.5 meters per second (7 knots), making it one of the fastest currents globally during its peak. This strong flow transports up to 60-70 Sverdrups (a unit of volume transport), comparable to the Gulf Stream.
As the monsoon shifts to the Northeast (winter), the current weakens considerably, reverses direction southwestward, or even disappears entirely. This dramatic transformation, occurring twice annually, is a direct consequence of the changing monsoon winds.
Ecological and Climatic Significance
The Somali Current’s unique behavior profoundly impacts the marine ecosystem and regional climate. During the Southwest Monsoon, the strong northeastward flow, combined with the Coriolis effect, drives intense coastal upwelling. This process brings cold, nutrient-rich water to the surface, fueling massive phytoplankton blooms. The Somali Current region is the only major upwelling system found on a western ocean boundary.
This nutrient-rich environment supports an incredibly productive marine ecosystem, sustaining diverse fish populations. Upwelling leads to lower coastal sea surface temperatures, influencing regional weather patterns. The dynamic interplay of the current and monsoons makes this area a significant contributor to global marine biological productivity and a crucial fishing ground for local communities.