How do the Pacific trade winds affect surface currents?

The Pacific trade winds are a primary driver of surface water movement in the Pacific Ocean. By blowing constantly across the equatorial region, these winds push vast volumes of water westward, creating the North Equatorial Current and the South Equatorial Current.123

This westward transport of water raises the sea level in the western Pacific. In the doldrums—the area near the Equator where strong, constant winds are absent—this difference in sea level causes water to flow back eastward, forming the Pacific Equatorial Countercurrent.13

The trade winds also influence vertical water movement. Stronger trade winds push warm surface water away from the coast of South America, which stimulates upwelling—the process where cold, nutrient-rich deep water rises to the surface. Conversely, when trade winds weaken, as occurs during El Niño events, this upwelling is dampened, which can significantly impact marine ecosystems and regional climates. During La Niña phases, the trade winds intensify, strengthening both the westward currents and the upwelling process.43