During which event does the eastern South Pacific surface temperature drop below average, usually at end of ENSO?

During which event does the eastern South Pacific surface temperature drop below average, usually at end of ENSO?

• A. La Nina
• B. Southern Oscillation
• C. North Atlantic Deep Water
• D. Surface Current

Answer: (A)

La Niña is the cool phase of ENSO, where the eastern South Pacific surface waters become cooler than average. This typically follows El Niño, bringing a shift back toward cooler conditions. Stronger trade winds push warm water toward the western Pacific, which enhances upwelling of colder water along the eastern Pacific near the South American coast. That upwelling lowers the surface temperature in that region, producing the observed drop below average. The other options describe atmospheric or unrelated ocean features, not a systematic cooling event in the eastern Pacific.

La Niña is the cool phase of ENSO, where the eastern South Pacific surface waters become cooler than average. This typically follows El Niño, bringing a shift back toward cooler conditions. Stronger trade winds push warm water toward the western Pacific, which enhances upwelling of colder water along the eastern Pacific near the South American coast. That upwelling lowers the surface temperature in that region, producing the observed drop below average. The other options describe atmospheric or unrelated ocean features, not a systematic cooling event in the eastern Pacific.