El Niño is associated with warming of surface water in which region of the Pacific Ocean?

• A. Western Pacific
• B. Central and eastern Pacific
• C. Southern Pacific
• D. Northern Pacific

Answer: (B)

El Niño is defined by a warming of surface waters in the equatorial Pacific, especially in the central and eastern portions. This occurs when the trade winds weaken, allowing warm water that normally pools in the western Pacific to spread eastward. The result is higher sea surface temperatures along the equator from near the dateline to the coast of South America, with the strongest anomalies in the central to eastern Pacific. This eastward warming also suppresses the upwelling of cool, nutrient-rich water off Peru, helping drive the global weather patterns associated with El Niño. The key point is that the notable warming during El Niño concentrates in the central and eastern Pacific, not the western, southern, or northern regions.