What is the primary cause of ocean currents?

The primary cause of ocean currents is primarily linked to wind and Earth's rotation. Wind generates surface currents by exerting a force on the water, causing it to move across the ocean's surface. This effect is enhanced by the rotation of the Earth, known as the Coriolis effect, which causes moving water to turn and twist in specific patterns. As a result, ocean currents tend to flow in circular patterns, known as gyres, which are influenced by the wind directions and the Coriolis effect.

While solar radiation does play a role in heating the oceans and can indirectly influence local currents by changing water temperature, it is not the driving force behind the movement of water across larger scales. River inflow can impact local salinity and may influence nearby currents but doesn't serve as a primary causative factor for ocean currents as a whole. Additionally, Earth's tectonic activity affects the seafloor and can lead to changes in ocean basins over geological timescales, but it does not directly drive the movement of water in the ocean as wind and rotation do.