El Nino

El Niño is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean. El Nino is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).

  • La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the region’s surface waters. El Niño and La Niña are considered the ocean part of ENSO, while the Southern Oscillation is its atmospheric changes
  • Led by the work of Sir Gilbert Walker in the 1930s, climatologists determined that El Niño occurs simultaneously with the Southern Oscillation.
  • The Southern Oscillation is a change in air pressure over the tropical Pacific Ocean. When coastal waters become warmer in the eastern tropical Pacific (El Niño), the atmospheric pressure above the ocean decreases. Climatologists define these linked phenomena as El Niño-Southern Oscillation (ENSO).

Effects of El Nino:

El Nino has an impact on ocean temperatures, the speed and strength of ocean currents, the health of coastal fisheries, and local weather from Australia to South America and beyond. El Nino events occur irregularly at two- to seven-year intervals. However, El Nino is not a regular cycle, or predictable in the sense that ocean tides are.

El Nino was recognized by fishers off the coast of Peru as the appearance of unusually warm water. We have no real record of what indigenous Peruvians called the phenomenon, but Spanish immigrants called it El Nino, meaning “the little boy” in Spanish. When capitalized, El Nino means the Christ Child, and was used because the phenomenon often arrived around Christmas


What is Upwelling?
In order to understand the development of El Niño, it’s important to be familiar with non-El Niño conditions in the Pacific Ocean. Normally, strong trade winds blow westward across the tropical Pacific, the region of the Pacific Ocean located between the Tropic of Cancer and the Tropic of Capricorn. These winds push warm surface water towards the western Pacific, where it borders Asia and Australia.
Due to the warm trade winds, the sea surface is normally about .5 meter (1.5 feet) higher and 45° F warmer in Indonesia than Ecuador. The westward movement of warmer waters causes cooler waters to rise up towards the surface on the coasts of Ecuador, Peru, and Chile. This process is known as upwelling.
Consequences of Upwelling:
  • Upwelling elevates cold, nutrient-rich water to the euphotic zone, the upper layer of the ocean.
  • Nutrients in the cold water include nitrates and phosphates. Tiny organisms called phytoplankton use them for photosynthesis, the process that creates chemical energy from sunlight. Other organisms, such as clams, eat the plankton, while predators like fish or marine mammals prey on clams.
  • Upwelling provides food for a wide variety of marine life, including most major fisheries. Fishing is one of the primary industries of Peru, Ecuador, and Chile. Some of the fisheries include anchovy, sardine, mackerel, shrimp, tuna, and hake.
  • The upwelling process also influences global climate. The warm ocean temperature in the western Pacific contributes to increased rainfall around the islands of Indonesia and New Guinea. The air influenced by the cool eastern Pacific, along the coast of South America, remains relatively dry.
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