Final answer:
Surface currents are primarily caused by the wind, which transfers energy to the surface water, affecting the flow of currents. Other factors include the Earth's rotation, water density changes, and significant climate events like El Niño.
Step-by-step explanation:
Surface currents in the ocean are primarily caused by the wind. These currents result from the friction between the wind and the surface water, where the wind's energy is transferred to the water, leading to the creation of currents. The patterns of these currents are further influenced by the Earth’s rotation through the Coriolis effect, which modifies the direction of the water flow.
Additionally, factors like the density of water, which can change due to differences in temperature and salinity, also contribute to ocean upwelling and free or natural convection in the ocean. During an El Niño event, a warm ocean current off the west coast of South America can have significant impacts on global weather patterns.
Overall, the interplay between wind, water's thermal properties, Earth's rotation, and global climate dynamics governs the behavior of surface ocean currents.