What Is El Nino
By guest writer, Sarah F.
What is El Nino?
El Nino is the warming of water surfaces of the tropical Pacific Ocean every three to six year. While some El Ninos are stronger than others, all of them can have worldwide weather effects.
The fishermen who fish off the coast of South America have known about this phenomenon for centuries. El Nino usually occurs near the Christmas season and was given its name as a result. In Spanish, El Nino means “the little boy” or “Christ Child.” These episodes were often linked to large reductions in sea catches and flooding rains. The fishes would virtually vanish and the fishing business would come to a standstill.
The Pacific Ocean is a vast open space and receives much more sunlight than any other region on Earth. Much of this sunlight is then stored in the water as heat. In a typical, non El Nino year, the trade winds along the equator in the Pacific flow from east to west.
As they do, the water below moves westward as well resulting in a larger, deeper pool of water in the west (just east of Indonesia and northeast of Australia) than in the east. Since nature abhors a vacuum, it has to do something in the east to replace the displaced water. As a result, in the east, a process called upwelling takes place – cooler water from the ocean depths rises to the surface. This creates an east-west temperature gradient along the equator known as a thermocline tilt.
So, if what is described above is normal, what is El Nino like?
With the onset of an El Nino, the trade winds begin to weaken and less water is pushed westward. As a result, the waters in the central and eastern Pacific will warm by several degrees and the delicate thermocline tilt diminishes. While these winds are usually replenished by the Asian summer monsoon, sometimes this is not the case and the winds will actually reverse and blow from west to east.
When this happens, the ocean responds by warming in the east. These warm waters can actually extend some 300 feet deep, preventing any cold water from coming close to the water’s surface. On average, the waters will warm by three to five degrees Fahrenheit, but in some areas it can be more than ten degrees warmer than normal.
When the water warms, it expands causing sea levels to rise anywhere from a few inches to more than a foot. However, in the western Pacific, the water levels will drop just as much. This can actually result in reefs growing on higher lands being exposed and destroyed.
Do you know what is El Nino’s effect?
This seemingly simple reversal in the direction of a natural climate process can have widespread effects. Areas that are normally adapted to one type of climate becomes suddenly subjected to violently different conditions. For example, normally wetter places like Indonesia and Australia could become dryer and warmer. Normally dry places like western South American and southwest United States could become a lot wetter than normal.
In addition, the disruption of normal weather patterns can result in economic consequences, especially for fishermen, whose sea catch is very much dependent on sea and weather conditions. When upwelling (often linked to nutrient-rich water that rises from the sea bed) is reduced, sea catch reduces. The wetter conditions in normally dry lands have also been linked to increase incidences of epidemic diseases, such as malaria.
With regards to what is El Nino caused by, some scientists believe that warmer ocean temperatures due to global warming actually increase the intensity and frequency of El Nino — it now occurs every two to three years.
An alternative explanation about what is El Nino linkage to global warming suggests that the increased land evaporation from higher global temperatures might be increasing the moisture in the air, thus intensifying the storms and floods brought by El Nino.
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