El Niño is a current of warm ocean water. It occurs about every 5-7 years and may last from a few months up to a year or longer.
Why “El Niño?”
This current is called El Niño (meaning male child in Spanish) because it generally occurs in December/January. The relation to the term “male child” comes from the custom of celebrating the birth of Jesus Christ during the month of December. Fishermen gave the current this name when they noticed the change in water temperature and how it affected marine life.
What Causes El Niño?
The cause of the El Niño current has a lot to do with trade winds. Trade winds normally pull warm surface water to the west, that is why the sea level in Indonesia is normally around 50 centimeters higher than it is on the coast of South America. When these trade winds die down the normal oceanic currents are thrown off so the warm water in the west can flow back toward South America.
During a “normal” year when the trade winds pull the warm water to the west an upwelling of cold nutrient rich water know as the Humboldt Current flows into the waters of the Galapagos. Without help from the trade winds the warm nutrient depleted waters of El Niño take the place of the Humboldt current causing a lot of damage to marine life and the animals that feed on it.
What Are The Effects of El Niño on the Galapagos?
The effects of El Niño are seen most drastically along the equator because the warm water along with it’s warm moist air patterns are not pushed out. This can cause heavy rainfall and flooding in Ecuador (the Galapagos) and Peru, while at the same time causing droughts in Indonesia and Australia.
While the increase rain fall due to El Niño can benefit the plant life and some of the land animals in the Galapagos, it has a very negative effect on the marine life. The fish and algae that benefit from the nutrient rich cool waters of the Humboldt current die off. This means that sea birds don’t have enough food so they can not raise young. Marine iguanas can not find enough algae to eat and suffer, or die because of it. Fur seals and sea lions also suffer due to lack of food.
The causes of El Niño are not yet totally understood. Some occurrences of El Niño are longer and have much more drastic effects than others. The last extreme occurrence lasted for a year in 1982-1983.
The 1997 El Nino seen by TOPEX/Poseidon. Image copyright NASA, considered in the public domain.