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What is El Niño, the event contributing to South Africa’s current drought?

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By Jacqueline Roux
I am sure that you have by now heard of El Niño, a climatic event affecting the globe, one of the reasons behind the extreme loss of crops and livestock in South Africa and the cause of national outcry in the last year. If you are in need of a quick overview of what it is, feel free to read further.

El Niño, dubbed the “boy Christ-Child” due to the presence of a weak, warm ocean current that flows past the west coast of South America at Christmas, is associated with large climatic warmings that occur across the globe. It represents the warm phase of ENSO, the El-Niño Southern Oscillation, whereas La Nina, its colder opposite forms part of the cold phase. The definition of El Niño according to the Oxford Advanced Learner’s Dictionary is “an irregularly occurring and complex series of climatic changes affecting the equatorial Pacific region and beyond every few years, characterized by the appearance of unusually warm, nutrient-poor water off northern Peru and Ecuador, typically in late December”.

El Niño is a cyclic event which affects the global climate every 3 to 5 years, for approximately nine to 12 months. The start of the cycle is represented by an eastwards shift of warm water along the equator in the Pacific Ocean towards the north-west coast of South America. The warm water is usually located around the Philippines towards the west, however during an El Niño event it replaces cold water along South America’s western coastline. Associated climatic changes include weakening of the trade winds and increased storm activity towards the east, which forms a connection between the atmosphere and ocean.

Frequent and more intense thunderstorms occur in South America at this time, due to evaporation fuelling the atmosphere with moisture from the warmer ocean water. The change in the location of the rain, causes a change in the Walker Circulation which in turn causes a change to the global climate. Weaker trade winds are less capable of blowing warm Pacific waters as far west as usual, which causes the warm water to pool closer to South America, leading to a sea level decrease at Indonesia and the Philippines and an increase at Ecuador.

ENSO

Figure 1: Left – trade winds push warm water towards the west and an upwelling of cold waters occurs on the west coast of South America during normal conditions. Right – weaker trade winds cause the warm water to pool and move east towards the west coast of South America causing increased storm activity closer to its coastline. Thermocline represents boundary between warm and lower cold water. Dashed line represents Walker Circulation. Note: Australasia is to the left of each diagram and South America to the right of each diagram Sourced from  http://oceanworld.tamu.edu/students/elNiño/elNiño1.htm

It is believed that a specific cause of El Niño has not been identified due to the uniqueness of each El Niño event but there are tell-tale signs that can be observed to determine the possibility of an approaching El Niño event. These include: observing temperature shifts towards the east in the upper 200 metres of the Pacific Ocean and measuring storm activity in the region of Peru and Ecuador. Evidence of these events can be dated back millions of years and are found within cores taken from ice and even coral and tree rings.

Despite El Niño bringing more rain to the South American coast, it negatively affects fisheries and marine ecosystems in that area. Fish thrive in the upwelling cold nutrient-rich water along the South American west coast during the years not affected by an El Niño, however the pooling of warmer water so close to the South American coastline forces the cold water further down into the ocean, creating a less supportive environment for a marine ecosystem, which subsequently has to migrate either north or south to colder water.

Where tropical cyclones are intense along the Pacific Ocean during an El Niño, hurricanes become much less frequent over the Atlantic Ocean due to stronger wind-shear and more stable air caused by El Niño. Indonesia and the Philippines experience less rainfall and further drought conditions prevail in southern Africa, Australia and India. However, countries along the South American east coast especially Mexico can experience torrential downpours and increased hurricane activity during an El Niño event.

South Africa has been observably affected by El Niño, and according to the AllAfrica website, 2015 has seen the worst drought since 1982. Five provinces, including KwaZulu-Natal and the North West Province have been affected by drought conditions triggered by El Niño, reportedly costing crop farmers $600m. Government places emphasis on focusing production rather on irrigation, which will lead to new infrastructure and has expressed interest in importing more than 4 million tonnes of maize to accommodate that which was lost.

According to the South African Weather Service, El Niño does not always cause a drought in South Africa as soil moisture content, groundwater resources and the effect of the Indian Ocean can sometimes lessen the impacts of the event. At this time however, we are experiencing a drought most likely brought on by El Niño and global warming, which could last until autumn this year. It thus becomes of paramount importance that we, as South Africans do something on our part to minimize the effects El Niño has and will have on our country. So while we wait for the trade winds to pick up again, air pressure patterns to stabilize and just generally waiting for this disastrous ‘boy’ to let up, we can adopt eco-friendly ways of conserving water in and around our households as well as helping those humans and animals suffering in the disaster areas.

 

Jacqueline Roux is a Durban-based student who is currently completing her honours in Engineering and Environmental Geology at UKZN. She has a passion for environmental conservation and community development.

 

Disclaimer: The views expressed here are solely those of the author in her private capacity and do not necessarily represent the views of FTFA


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