What is the primary cause of ocean currents?

The primary cause of ocean currents is wind direction. Winds blowing across the surface of the ocean exert a force on the water, causing it to move. This movement is heavily influenced by the prevailing wind patterns, which are created by the uneven heating of the Earth's surface from the sun. Additionally, the Coriolis effect, a result of the Earth's rotation, further directs the flow of these currents, contributing to their circular patterns known as gyres.

While the rotation of the Earth does play a significant role in influencing the paths of ocean currents, it is the initial force from the winds that generates the currents themselves. Factors like water temperature and salinity certainly affect water density and can influence current circulation patterns, but they are not the primary driving force behind the movement of ocean currents. Thus, wind direction stands as the most essential component in initiating and sustaining ocean currents.