El Nino and South America
El Niño is a climate pattern that describes the unusual
warming of surface waters along the tropical west coast of
South America. 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. El Niño events occur irregularly
at two- to seven-year intervals. However, it is not a regular
cycle, or strictly predictable in the sense that ocean tides
are.
El Niño has long been recognized by fishers off the coast of Peru as the yearly appearance of
unusually warm water in the Pacific Ocean. The name El Niño, meaning the "little boy" in
Spanish, was used because the phenomenon often arrived around Christmas.
Peruvian scientists later noted that more intense climatic changes occurred at intervals of
several years, shifting the meaning of El Niño to describe these irregular and intense events
rather than the annual warming of coastal surface waters.
Upwelling
In order to understand the development of El Niño, its important to be familiar with non-El
Niño conditions in the Pacific Ocean. Normally, strong trade winds blow west 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 toward the west Pacific. The western Pacific
Ocean borders Asia, the islands of Oceania, and Australia.
Due to the warm trade winds, the sea surface is normally about 1.5 feet higher and 14 degrees
Fahrenheit warmer in Indonesia than Ecuador. The westward movement of warmer waters
causes cooler waters to rise toward the surface along the coasts of Ecuador, Peru, and Chile.
This process is known as upwelling.
Upwelling lifts this cold water, rich in nutrients to the upper layer of the ocean. Tiny organisms
thrive in this cool ocean water. Upwelling provides food for a wide variety of marine life, and
the tropical South American coastline is home to some of the world's richest fisheries. Fishing
is one of the primary industries of Peru, Ecuador, and Chile.
Upwelling also influences global climate. The process increases rainfall over the western
Pacific's warmer waters, such as the islands of Indonesia and New Guinea. The eastern Pacific,
along the coast of South America, remains relatively dry.
El Niño Events
During an El Niño event, westward-blowing trade winds weaken along the Equator. These
changes in pressure and wind speed cause warm surface water to move eastward along the
Equator, from the western Pacific to the coast of South America.
The warm water builds up, or thickens, along the coasts of Ecuador, Peru, and Chile. This thick
layer of warm water does not allow for normal upwelling to occur. Without this upwelling of
nutrient-rich cold water, the eastern Pacific can no longer support its normal ecosystem. Fish
populations die or migrate. El Niño has a devastating impact on the Ecuadorian and Peruvian
economies.
El Niño also produces widespread and sometimes severe changes in climate. Rainfall increases
drastically in Ecuador and northern Peru, which normally have fairly arid (dry) climates. Coastal
flooding and erosion are common El Niño events. Rains and floods may destroy homes, schools,
hospitals, and businesses. They also limit transportation and destroy crops.
As El Niño brings rain to South America, it brings droughts to Indonesia and Australia. These
droughts threaten water supplies, as local reservoirs dry up and rivers carry less water.
Agriculture, which depends on water for irrigation, is threatened.
Stronger El Niño events also disrupt global atmospheric circulation. Global atmospheric
circulation is the large-scale movement of air that helps distribute thermal energy across the
surface of the Earth.
The eastward movement of heat in the ocean and atmosphere causes unusually severe winter
weather at the higher latitudes of North and South America. Heavy rain along Central
America's Pacific coast is common in El Niño years. Regions as far north as the U.S. states of
California and Washington may experience longer, colder winters because of El Niño.
El Niño has diverse impacts on tropical storms in the Pacific and Atlantic. Most meteorologists
think El Niño events contribute to more tropical storms in the eastern Pacific, while
contributing to a reduced number of hurricanes in the Atlantic and Gulf of Mexico.