El Niño
Tags: Climate Change, Wind, Weather, Climate, El Nino

El Nino were observed as early as the 1600s. In the 1920s The British scientist Sir Gilbert Walker empirically identified that some notable climate anomalies — changes in atmospheric pressure and circulation — happen around the world every few years, he invented the term for those climate oscillations, “the Southern Oscillation.” El Nino is a naturally occurring event in the equatorial region which causes temporary changes in the world climate. Originally, El Nino was the name used for warmer than normal sea surface temperatures in the Pacific Ocean off the coast of South America. Now, El Nino has come to refer to a whole complex of Pacific Ocean sea-surface temperature changes and global weather events. The ocean warming off South America is just one of these events. Anglers off the west coast of South America were the first to notice appearances of unusually warm water that occurred at year’s end. The phenomenon became known as El Niño because it tended to occur around Christmas time. El Nino is Spanish for “the boy child” and is named after the baby Jesus.

In normal conditions, trade winds blow in a westerly direction along the Equator. These winds pile up warm surface water in the western Pacific, so the sea surface is as much as 18 inches higher in the west of the Pacific than in the eastern Pacific. These trade winds are one of the primary sources of fuel for the Humboldt Current. The Humboldt Current is a cold ocean current which flows north along the coasts of Chile and Peru, then turns west and warms as it moves out into the Central Pacific. So, the typical situation is warmer water in the western Pacific, cooler in the eastern. In an El Nino, the equatorial westerly winds diminish. As a result, the Humboldt Current weakens, and this allows the waters along the coast of Chile and Peru to warm and creates warmer than usual conditions along the coast of South America. As far as known, other forces, such as volcanic eruptions (submarine or terrestrial) and sunspots, do not cause El Niño’s.

El Niño’s occur irregularly approximately every 2 to 7 years. Warm water generally appears off the coast of South America close to Christmas and reaches its peak warmth in the eastern Pacific during the late fall of the following year. After peaking, the waters will tend to cool slowly through the winter and spring of the next year. Effects can be felt continually around the globe for more than a year, though this is generally not the case in any one place.

A strong El Niño is often associated with flooding rains and warm weather in Peru, drought in Indonesia, Africa, and Australia, torrential downpours and mudslides in southern California, a mild winter in the northeast, and fewer hurricanes in the southeast. Keep in mind that these effects are not guaranteed, but an El Niño makes these conditions more likely to happen.

In non-El Niño years, upwelling of deep, cold ocean water brings up nutrients that lie near the bottom. Fish living in the upper waters feed plankton that is dependent on these nutrients. Kelp forests also depend on cold, nutrient-rich water for survival and growth. An El Niño reduces the upwelling of cold water off the coast of the Americas. When this happens, fish either die or migrate into areas where they will find more to eat. With the fish gone, sea birds that depend on them may die or go elsewhere. Storms and ocean swell often destroy kelp forests. Off California, fish populations may also be reduced. Marine mammals, such as seals and sea lions, that feed on fish may be affected. Californians may see an increase in dead and live strandings of seals and sea lions along the coast, and poor seal and sea lion pup survival at island breeding sites. However, despite the increased number of deaths of marine mammals during an El Niño, scientists report the long-term growth rate for California sea lions and harbour seals to be 6 to 10 % annually. An occasional increase in stranding’s or deaths of these animals is not a threat to their overall population.

In California, warmer than usual ocean temperatures mean fishes usually found off Mexico, such as yellowfin tuna and dorado, are more common off southern California. However, bait, such as anchovy and squid, may travel to the north, and some game fish, such as white seabass and California halibut, may follow them.

In the tropical Pacific Ocean, the National Oceanic and Atmospheric Administration operates a network of buoys that measure temperature, currents and winds in the equatorial band. The collected data are evaluated by complex computer models designed to predict an El Niño. Even these complex models, however, cannot forecast the same intensity or duration of an El Niño, nor can they predict how areas will be affected.