The El Niño Effect

THE EL NIÑO EFFECT – FROM THE ARCHIVES

Reports are starting to emerge of El Niño conditions in the tropical Pacific Ocean.

Read FOSFA’s 2004 article on the El Niño phenomenon.

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THE EL NIÑO EFFECT

Periodically, and seemingly with more frequency, the Commodities Trade is hearing of the effects of El Niño on production of a wide range of crops, grown throughout the Pacific Rim, and the consequential effects on markets.

A disruption of the ocean-atmosphere system in the tropical Pacific, El Niño! “The Boy Child”, a name traditionally used by Peruvian anchovy fisherman – a reference to the Christ child – to describe the appearance, around Christmas, of a warm ocean current off the South American coast.

The El Niño affects traditional fisheries in Peru and Ecuador. In most years, colder nutrient rich water from the deeper ocean is drawn to the surface off the coast producing abundant plankton, the food source for one of the world’s most productive fisheries. However, when this upwelling of water weakens as in El Niño affected years, warmer, low nutrient rich water spreads along the coast, and the catch is severely affected.

Today, the term no longer refers to this local seasonal current shift but to part of a phenomenon known as El Niño-Southern Oscillation (ENSO), a continual but irregular cycle of shifts in ocean and atmospheric conditions that causes abnormal weather around the globe.

The perception of, and the reality of the term “abnormal”, must vary widely. For the peoples of Indonesia, Australia and South Eastern Africa, the El Niño phenomenon delivers severe droughts, which can result in devastating forest fires. The inhabitants of Peru, Ecuador and California will associate the effect with torrential rain storms that trigger serve flooding and deadly mudslides.

In normal non-El Niño conditions, the trade winds blow towards the west across the tropical Pacific. These winds pile up warm surface water in the west Pacific, so that the sea surface is about half a metre higher at Indonesia than Ecuador. During an El Niño event, these winds relax causing a depression in the thermocline in the eastern Pacific and an elevation in the west.

Come to refer to the more pronounced weather effects associated with the air above the eastern and central Pacific Ocean, El Niño has a counterpart – La Niña, “The Little Girl” sometimes called El Viejo, anti-El Niño, or “a cold water event”. La Niña is associated with a cooling of the eastern tropical Pacific.

El Niño and La Niña events tend to alternate about every three to seven years. However, the time from one event to the next can vary from one to ten years.

Much research has been and continues to be directed at predicting the start of such events, but factors leading to the end of an El Niño event are still not entirely clear and have yet to be established.

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