by Austin Yeung 2015-06-13
El Niño, ‘the Christ Child’, was first named by fishermen in Peru during Christmas when they noticed unusual warm currents affecting the Pacific coastline of South America. It is an anomaly – a prolonged warming of the central and east-central Pacific Ocean sea surface temperatures (SST).
El Niños often happen in intervals between two to seven years, and last nine months to two years. When this El Niño warming happens for only a brief 7-9 months, it is classified as an El Niño “condition,” whereas when the El Niño period lasts longer, it is known as an “episode.”
Coral reefs, rainforests of the oceans, are susceptible to coral bleaching as a result of high water temperatures. Bleaching occurs when coral tissues expel algae, known as zooxanthellae, that reside in the coral, and die. The entire coral reef then turns white as if it were bleached. That’s why coral scientists pay attention to such ocean warming events as El Niño.
Currently, NOAA just declared that the most recent El Niño commenced in March 2015. The latest forecast showed a 90% chance of the El Niño continuing in the fall and an 85% chance into winter of 2015/16. Many anticipated a stronger El Niño since the 1998 El Niño occurrence. With an increase of 4°C in SST, the 1998 happening of the El Niño undersizes the current El Niño, which saw a greater than 1.9°C SST. Although this is not a weak El Niño appearance, it is not a strong one either.
El Niños occur every few years, often leading to drastic weather change. Disrupting the ocean atmosphere in the tropical Pacific, it affects the weather all around the globe. Other consequences, often caused by more powerful El Niños, can cause increased rainfall, which then leads to destructive flooding and droughts, sometimes even a devastating fire.
Trade winds are affected during the El Niño period, where they usually blow west towards Indonesia, relax and settle down in the central and western Pacific. During normal years, warm water would build up in the Western Pacific Ocean and cold water would well up in the Eastern Pacific Ocean, off South America’s western coast. This upwelling of cold water is nutrient-rich, fostering marine productivity.
During El Niños, the opposite happens. Weak trade winds allow warm water to linger along South America’s western coast. The usually cool water warms significantly as the upwelling of cold water along the Peruvian coast weakens and supply of nutrient-rich water is cut off.
The cut-off of nutrient-rich waters lead to a decline in fisheries all around the Pacific Ocean. As the Pacific’s warmest waters moves eastward, the hot-humid waters which fuels thunderstorms accompanying it, leading to drastic weather changes in North and South America.
Not only are El Ninos monitored by scientists, economists and traders also pay attention because of how they may affect global weather patterns, and therefore commodity prices.
To learn more, you can find an excellent depiction of the El Niño Southern Oscillation (ENSO) here.