A severe drought causes starvation in Africa. Flash floods kill thousands in the Caribbean. The hottest temperatures in years are witnessed in California. Thousands of marine species die off the coast of South America. These aren’t scenarios out of a fictional science thriller. All of these things are real, and a direct result of a natural phenomenon that occurs in the waters of the Pacific Ocean.
Water temperatures in the southern Pacific Ocean fluctuate on a regular cycle. When there are extreme changes of sea surface temperatures (SST), it is a process known as the El Nino-Southern Oscillation (ENSO). The exact causes of this oscillation is unknown, but the changes are very noticeable and periodic. On average, a warm phase will occur every 7 years. During a warm phases of the ENSO, the area of warm water is greater in temperature and size, and is shifted east towards South America. During the cold phase, this pool of warm water is closer to Australia. The result is the redistribution of precipitation and surface winds.
Off the coast of South America, there is very cold water as a result of upwelling. This, in combination with the wind direction, causes there to be a desert climate along the west coast. During the warm phases however, this cold water is replaced with much warmer water. There are multiple results from this. The more noticeable is a dramatic increase in precipitation in the arid zones of western South America, sometimes leading to deadly floods. The second is the destructive effects on the marine habitats, which are used to cold water to supply nutrients. With more precipitation falling over the west coast, that means someplace else is not getting their normal precipitation. This redistribution results in drought for many places that expect a certain amount of annual precipitation.
The affects of El Nino has been tied with changes in weather patterns all over the world. Small increases in SST in the Pacific have be linked to increases of surface temperatures over Northern America. Other effects have been the increase of destructive storms throughout the world. The most extreme El Nino on record occurred during 1982-1983, and resulted in many destructive events throughout the world. Some of those include: drought in Africa and Australia, a rise in sea level off California, increased cases of deadly diseases, floods in the tropics, the death of many animals, and much more.
While the exact mechanism of the ENSO cycle is still unknown, its affects are real and potentially devastating. The Earth’s atmosphere and ocean are complex systems that are woven tightly together. Small changes in one can lead to extreme changes in the other.
