El Niño a ocean-atmosphere phenomenon. El Niño is an important temperature fluctuation in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from the Spanish for “the little boy,” refers to the Christ child, because the phenomenon is usually noticed around Christmas time in the Pacific Ocean off the west coast of South America.
El Niño is associated with floods, droughts, and other disturbances in a range of locations around the world. El Niño is the most prominent known source of variability in weather and climate around the world, though not all areas are affected. El Niño has signatures in the Pacific, Atlantic, and Indian Oceans.
The first signs of an El Niño are:
- Rise in air pressure over the Indian Ocean, Indonesia, and Australia
- Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean
- Trade winds in the south Pacific weaken or head east
- Warm air rises near Peru, causing rain in the northern Peruvian deserts
- Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.
El Niño’s warm current of nutrient-poor tropical water, heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current, also known as the Peru Current, which support great populations of food fish. In most years the warming lasts only a few weeks or a month, after which the weather patterns return to normal and fishing improves. However, when El Niño conditions last for many months, more extensive ocean warming occurs and its economic impact to local fishing for an international market can be serious.
The Coriolis Effect is the apparent deflection of a moving object due to the rotation of a greater object. On Earth, the Coriolis Effect deflects ocean currents north of the equator to the right and currents south of the equator to the left.
Gyres are large mounds of water created by the Coriolis Effect. These gyres produce large circular currents in all of the ocean basins. Gravity keeps these mounds from growing too high by pulling the water back down toward the center of the Earth.
The Coriolis Effect directly influences ocean surface currents. Currents on the western coast of continents are usually cold and currents on the eastern coast are warm because they originate from the equator. This is important because the movement of these currents distributes heat from the equatorial regions of the Earth to cooler regions.