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El Niño phenomenon and climate prediction

Posted: Sunday, October 06, 2002

Predicting climate can be a bit confounding to say the least. Historical weather records can tell you part of the story, but there is so much more to consider in our Earth and atmospheric system.

Global warming, ozone layer holes, shrinking polar ice caps, large volcanic eruptions, atmospheric pollution, ocean currents and recent weather patterns are just a few of the things that can influence climate. Many of these phenomena have just been discovered over the past three or four decades.

Though much has been done to monitor all of this, the true research goal is to determine how all these processes interact. Only then will climate prediction become more viable than a look at historical weather records. You could say that the science of climate prediction (seasonal and yearly forecasts) is still in its infancy.

El Niño is one phenomenon where a lot of good climate research has been completed. The term El Niño is Spanish for "the little boy" or "the Christ Child." It was originally used by fishermen along the coasts of Ecuador and Peru to describe a period of several months where warmer than normal sea-surface temperatures occurred in the eastern Pacific Ocean.

This warm spell of the ocean waters typically began around Christmas, hence the Christ Child reference. When the ocean becomes warmer, these fishermen fell on hard times because they could not catch as many fish. They also noticed that more frequent and heavier rains occurred. This irregular cycle of ocean warming, torrential rains and hard luck fishing occurred anywhere from two to 10 years apart.

In Southeast Alaska the impacts of El Nino are not as clearcut. Part of the reason is that little research has been completed on the relationship between El Nino and the climate of the Panhandle.

Another hypothesis is that perhaps we should be researching the influence of ocean currents closer to home. The Alaskan Current, which stretches across the North Pacific and Gulf of Alaska, might have more of an influence on our climate. Perhaps El Nino episodes can be related to subtle changes in the Alaskan Current and that in turn has a more direct impact on our climate. The extent of the sea ice in the Bering likely also has an influence here.

The research we have available to date suggests that recent El Nino winters are warmer and wetter than normal in Southeast Alaska. The milder winters have resulted in above normal rainfall and below normal snowfall at sea level.

During El Nino years, the typical easterly trade winds that occur along the tropical Pacific weaken. This directly reduces the easterly spread or swell of the sea surface waters along the equator.

Normally upwelling of cooler, deeper seas occurs along the coast of Ecuador and Peru to replace the warmer, surface water transported by that easterly swell. If the easterly swell ceases due to lighter trade winds, so does this upwelling along the coast. Nutrients that exist near the bottom of the ocean are no longer available and the fish populations of the region dwindle. The sea surface waters of the eastern Pacific turn warmer than normal due to that lack of upwelling.

Extensive research over the past several decades has proven direct relationships between El Nino episodes and climate extremes across the globe. Think of the Earth, its atmosphere and oceans, as one big system. The permutations of all the variables interacting in this big system are countless.

One thing that is evident, however, is that the larger the phenomena, the greater the influence it can have on this system. Volcanic eruptions, if large enough, can have far-reaching impacts on the world's climate. This is similar to El Nino. The greater the warming of the equatorial Pacific surface waters and the longer it lasts, the more pronounced the climate impacts are across the globe.

Current warming is taking place in the Pacific Ocean along the equator. An El Niño has developed and will continue into the spring of 2003. For many parts of the world El Nino means some sort of climate extreme is right around the corner.

Excessive drought and wildfires occur in Australia and Indonesia. Wetter than normal winters usually occur across the southern United States. Flooding events are common in California and in the Gulf of Mexico states. The northern portions of the Lower 48 typically experience mild winters with warmer than normal temperatures.

Climate prediction will improve with time. More and more viable research is being completed each year. Even here in Southeast Alaska seasonal and yearly forecasts will get better. Until that day arrives, continue to take it all with a grain of salt. Climate predictions may not always be right on, but they are the best we have for now.

Chris Maier is the warning coordination meteorologist at the National Weather Service Forecast Office in Juneau. Southeast Wild is provided by the Juneau Audubon Society.

Anne Post, Alaska Department of Fish & Game wildlife biologist and Pack Creek manager, will talk about the bears and other wildlife of Pack Creek at Juneau Audubon Society monthly meeting 7:30 p.m. Thursday, Oct. 10, at Dzantik'i Heeni Middle School.



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