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It’s January, so it must be El Nino

Bill Meredith

"An ecologist is something of a chartered libertine; he roams at will over the preserves of the plant and animal biologists, the physiologist, the behaviorist, the meteorologist, the geologist, the physicist, the chemist, and even the sociologist. He poaches from all these and from other established and respected disciplines."
Amyan MacFadyen, 1957.

(January, 2016) When I was a child, it puzzled me that Christmas always arrived on the 25th of December. At first, my parents told me it was because Santa Claus couldn’t get the toys all finished in his workshop any sooner. That made sense to me, because my Dad also had a workshop, and I knew it took time to make things. And I also knew Santa had to wait until winter, so there would be snow for his sleigh to run on. I actually knew people who had horses and sleighs then, and I knew it always snowed. Life was simple and reliable then.

That was then, but this is now. This year, the temperature was above 60< two or three times each week before Christmas; I played golf in each of the first three weeks, and would have in the fourth if it hadn’t rained. The news reported record snow and cold in Arizona, but here in Emmitsburg the only white to be seen was the plastic Santa Claus statues in people’s yards. The news was full of reports (some accurate and some not) about how El Nino is to blame for the changes in the weather. Life isn’t simple any more.

I’m not sure when I first heard of El Nino. It was not mentioned in any of my college or graduate courses in ecology, and it did not appear in standard ecology textbooks until the late 1980s. I do remember that I was teaching about it in my own course in the late ’60s, so I probably read about it some of the journals I subscribed to back then. I enjoyed teaching about it; it was complicated, but that was part of its fascination. It brought to mind Amyan MacFadyen’s definition of what an ecologist does. It made an amazing story.

The story begins in the Pacific Ocean, off the coast of Peru. This region was once the world’s largest fishery, and is still important source of anchovies, though overfishing has reduced it considerably. As far back as the 17th Century, Peruvian fishermen knew that every five or six years the water would get warmer and the anchovy population would die off; and since that usually happened around Christmas, it was given the name of "El Nino," which means "The Child" in Spanish. But it was not until early in the 20th Century that scientists began to understand how the El Nino phenomenon was caused by ocean currents.

You can begin to understand ocean currents if you imagine you are sitting in a chair at the equator. You would feel like you were sitting still; but since the earth turns around every 24 hours and the distance around the equator is about 25,000 miles, you actually are moving over 1,000 miles per hour toward the east! The water of the ocean rotates with the rest of the earth, but, being fluid, it tends to lag behind a bit. So if you were on a raft at the equator near South America, you would feel a current carrying you westward. The water flowing away from the coast has to be replaced (otherwise, it would leave a big hole in the ocean), so this draws a current of water northward along the coast of South America. The end result of this is that the entire southern half of the Pacific Ocean is made to turn slowly in a counter-clockwise direction. The same forces exist in the northern half of the Pacific; water is drawn southward from the coast of California, where it joins the westward flow, making the northern Pacific rotate in the clockwise direction. Therefore, the two halves of the ocean turn against each other like giant cogwheels.

As the current flows away from the Peruvian coast, it causes turbulence and mixing of the water near the shore, which brings up cold water from the ocean floor. This water contains nutrients that stimulate the growth of plankton, the basis of the anchovy food chain. We still don’t know all of the details of this mechanism, but every few years it gets disrupted and the upwelling zone moves offshore. When this happens the food chain loses its source of nutrients, so there is nothing to keep the plankton growing, and the anchovy population crashes. It takes a year or so to recover, and thus it causes severe economic problems for the people whose income depends on the fishery. Also, the change in the water temperature causes turbulence in the wind systems, and this spreads westward across the Pacific, producing more severe storms, typhoons, when it approaches the Australian, Asian and Indian land masses.

The current that flows northward along the western coast of South America was discovered around 1800 by Alexander von Humboldt. He was aware that the anchovy fishery collapsed every few years, and he also noticed that in many cases there were unusual weather conditions like droughts, floods, or extreme temperatures in places as far away as India, Europe and Africa, which occurred at the same times. Those weather extremes often led to crop failures, famines, and outbreaks of insect-borne diseases such as malaria. In many cases, wars resulted when people fought over limited food supplies, or groups of people were forced to migrate away from affected areas. Humboldt seems to have been the first to notice these coincidences; he noted that one cause of the French Revolution was unrest in the French working classes after a drought and crop failure which coincided with an El Nino event.

Over the next 150 years many other people called attention to coincidences like that; but the fact that two things occur at the same time in different places is not proof that one event caused the other. It was not until after World War II that submarine vessels were able to measure deep-water temperatures, movements and chemical changes with any degree of precision. Then, in the 1960s, satellite telemetry became available as a tool to measure atmospheric movements and temperatures all over the world, and hard evidence of a connection between El Nino events and changes of climate on a world-wide scale began to accumulate. It was discovered that a similar pattern of ocean currents occurs in the Atlantic; there is a northward flow of water along the west coast of Africa, and a major fishery off the west coast below the equator. Its effect is not as severe as El Nino because the Atlantic Ocean is smaller than the Pacific; but it does contribute to the instability of the world’s climate.

We all learned in Elementary School that the seasons are opposite in the Northern and Southern Hemispheres. Christmas comes on December 25 everywhere, but in Emmitsburg it is winter and in Peru it is summer. This means that when El Nino causes the upwelling of cold water to move away from the coast of Peru and be replaced by warm water coming from the California coast, it will be summer there and the atmosphere will be heating up. The prevailing winds will carry this warm air westward, accompanying the ocean current and adding to the instability of both air and water. It is a pattern that has probably been going on at least since the end of the Ice Age, 10,000 years ago; we are beginning to understand it, but we cannot control it.

A side note: Amyan MacFadyen died two months ago, at the age of 95.

Read other articles by Bill Meredith