El Nino Wreaks Havoc
The complex, interrelated geology of the Andes, the Atacama Desert, and the Atacama Trench all come together in the face of El Nino, a weather pattern that affects the whole planet. The microscopic plankton that grow in the sunlit waters of the upper ocean provide the foundation for the ocean's food chain, just as grass does on land. Some of the plankton that grow in the water near the surface sink to the bottom when they die. In shallow waters, a rich community of creatures lives on this rain of nutrients. But in deep, lightless places like the Atacama Trench, few bottom-dwelling creatures exist to harvest the drift of organic debris. So the nutrients accumulate in the trenches. Normally, prevailing winds blow down from the Andes across the Atacama Desert and on out to sea, which drives strong surface currents. These surface currents create an upwelling that brings nutrient-rich water up from deep in the Atacama Trench. This normally makes the seas off the coast of Chile heaven for fish, especially sardines and all the larger fish that eat them.
But every two to seven years, warm water sweeps in close to the coast, part of a global cycle in wind and ocean patterns. The warm water cuts off the nutrient-rich upwelling and devastates the fish, fishermen, sea birds, and sea lions, all of which are connected by the food chain. This warm surface current also generates a deluge of rainstorms, which batter the Andes and the coast of Chile. This pattern of periodic warm surface currents off the coast of South America has been dubbed El Nino. The cycle has persisted already for thousands of years, as demonstrated by the way in which the Inca built their cities and irrigation canals. Clearly, they had adapted to these cycles of drought and flood.
No one is quite certain what triggers El Nino, but it apparently connects to the failure of the trade winds at the equator. Those trade winds, in turn, are directly connected to the atmospheric circulation that produces deserts along about 0 degrees of latitude in both the Northern and Southern Hemispheres. For some reason, these trade winds periodically weaken and then reverse themselves. This causes more storms in the Pacific and southern North America, but decreases storms and hurricanes in the Atlantic.
The effects can be devastating. One terrible El Nino event brought drought in India between 1789 and 1793 and caused an estimated 600,000 deaths due to starvation. El Nino increases the odds of wildfires throughout the world and droughts in Indonesia, Eastern Australia, New Guinea, West Africa, and northern South America. The 1982–1983 El Nino caused floods and typhoons that killed ,000 people in the United States, Peru, Ecuador, Bolivia, Cuba, Hawaii, and Tahiti and brought drought elsewhere. Estimates put damages at a total of 13$ billion.