EL NINO

"As one, wet merchants turn their eyes towards the west

Trade winds falter, as if in dire consequence

Freezing fish to fry, fail to materialise

Christ-child, blood-warm current sends to touch the skies"

Ian Anderson (Jethro Tull), 'El Nino' (1999)

Useful sites for the phenomenon, also known as ENSO (El Nino Southern Oscillation) include the following:

We also provide handouts from a Geography Review resource pack, and a GeoPress factsheet from a couple of years ago. A personal archive of newspaper clippings has also been built up over the years, and this produces some good materials. Try also a search of online news archives can be carried out - there's no shortage of materials on El Nino as you'll soon find out.

El Nino is a reversal of the normal circulation of air and ocean currents in the Pacific Ocean: also known as ENSO: El Nino Southern Oscillation.

Could be defined as: "an anomalous widespread warming of the sea surface of the tropical East and Central Pacific"

Called El Nino by Peruvian fishermen as warm current appeared / happened around Christmas: was actually called El Nino de Navidad: 'Christ child'. Every 3-7 years it got worse, and affected their fishing yield. Occurs every few years and lasts about a year, and is accompanied by changes in atmospheric and weather patterns which extend beyond the immediate area.

The southern circulation becomes weaker, and trade winds die down. Warm water moves eastwards across the Pacific. This moves the position of the Jet stream, and areas which are normally dry become wet and vice versa.

The effects are strongly felt in Peru. The offshore waters are normally cold, due to the Humboldt Current. In an El Nino year, the water can be up to 8 degrees warmer, and this affects the amount of nutrients which well up from depth. As little as 1 degree above normal can affect the sea surface temperature, which affects the amount of evaporation and production of rain clouds. The nutrients are necessary for fish to feed on, which in turn are food for seabirds and mammals. The nutrients well up because the warm surface water is dragged off the shore by the trade winds, and cold water replaces it.

Typical effects include drought in some areas, increased precipitation in others causing floods, mudslides etc. Hurricanes are more common, for example on the Mexican coast where they are normally rare.

The effects of El Nino spread beyond the immediate area, as there is a knock-on effect on other areas. These larger scale effects are called tele-connections, and they have been blamed for changing weather conditions all along the Pacific coast and even as far as the Horn of Africa.

El Nino affects fish populations, and fish meal production (used to feed to poultry and livestock), which has global economic impacts.

The shift in winds would also affect the operations of aircraft as the upper air circulation is affected too.

When El Nino finally ends, an 'over-compensation' can occur, which results in La Nina: the opposite, but worse than the normal situation.

Need to investigate the effects of El Nino in Peru and other parts of S. America and the world.

As far as the exam goes: need to consider the effect of El Nino, and be able to answer the following questions:

Drought in Australia in 1980's was one side effect of El Nino. Cause was a periodic heating of the equatorial Pacific Ocean known as El Nino, the Child. Falls hardest on the eastern side of Australia - they are known locally as 'dries'. Many farmers in Australia have already spent time preparing for a dry period which they know will come sooner or later. This involves: deepening ponds which livestock use to drink from and drawing up plans for soil conservation. The first signs of an El Nino system is the decline in the HIGH pressure which normally sits over the Northern part of Australia around Darwin. This is sign that the southern oscillation is beginning.

There have been 10 El Nino events since WW2. The Trade winds falter, and the equatorial current reverses direction across the Pacific. Sea water temperatures rise, and a tongue of warm water extends along the equator. Each El Nino leads to billions of dollars of damage. The warm water layer, hundreds of feet thick prevents the cold ocean current from its upwelling. This leads to a reduction in the upwelling of nutrients from the Humboldt current, and the decline in the fishing industry. The cold water supports billions of plankton, which nurture fish and fish eating birds. This lead to a guano industry in Peru. For over 100 years, the country supported itself not by gold and silver, but bird excrement. Birds vanished along the coast and on the Galapagos islands. Coral declined.

The rains threatened Ecuador's banana plantations, and caused landslides which killed hundreds.

EL NINO / LA NINA