Climate change discusses, of course, changes in Earth’s climate. This includes things like warmer ocean temperatures and fiercer storm systems. Meteorologists on local news broadcasts attribute these destructive storms to something called “El Nino”. The gringa has been hearing this term for years and finds herself often saying, “Oh, yeah, El Nino.” But, when I actually take a moment to define what the heck El Nino is, um, I’m at a loss. Being familiar with climate change terminology doesn’t mean a person actually knows what that term means. So, here’s “El Nino 101” for some clarification.
El Nino is actually a weather system caused by oceanic temperature anomalies. El Nino specifically affects the equatorial Pacific region of Earth. It is defined by unusually warm ocean temperatures shifting eastward, traveling toward the coastal regions of South America. When trade winds shift from east to west, they drag warm surface waters westward. The warmer waters collectively pool in the waters east of Indonesia and northeast of Australia. As this is going on in the western Pacific, cooler waters are surfacing in the eastern Pacific which creates what is known as a “thermocline tilt”, an east to west ocean temperature gradation. This is Earth’s normal, healthy cycle of ocean agitation, much like stirring a pot to keep it from boiling over.
As spring breaks in the northern hemisphere, the trade winds abate, thus no more “stirring the pot” cooling effect. This causes the eastern Pacific to begin warming up, leveling out the thermocline tilt. If Asian monsoons do not restore the delicate temperature balance of the thermocline tilt, El Nino begins to happen. The warmer Indonesian waters begin to move eastward and the central Pacific waters continue to warm throughout summer and fall. The thermocline tilt disappears and warm surface waters prevent cooler, deeper waters from rising. This is called a “capping effect”. Capping results in central and eastern Pacific ocean regions warming by almost 5 degrees Fahrenheit, possibly even 10 degrees Fahrenheit.
Eastern Pacific warming causes ocean water to “expand” which means sea levels rise. This rise could be a few inches or even up to a foot. However, the opposite happens in the western Pacific. As warmer surface waters flow eastward, the western Pacific experiences lower sea levels that can expose upper levels of coral reefs, resulting in their bleaching and destruction.
All of this warmer water feeds the moisture in the air which collects in cloud systems. This extra moisture being added to Earth’s normal “rainfall” budget then results in massive storm systems. And that, in a nutshell, is the story of El Nino.
Image source: en.wikipedia.org