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Environment

Birth of El Niño?

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Something seems to be stirring in the western Pacific — a quickening that may herald the birth of El Niño. Should it actually happen, weather conditions in many places around the globe could be affected starting in the fall, including the possibility of wetter conditions for drought-plagued California, as well as a warmer globe overall. I put together the video above to help show in visual terms what's going on — and why the National Oceanic and Atmospheric Administration on Friday issued an El Niño watch, saying there is a 50 percent chance that one will develop this summer or fall. El Niño, meaning "the Little Boy" or "Christ Child" in Spanish, is one half of what's known as the El Niño-Southern Oscillation cycle. It is characterized by a periodic warming of the sea surface across the central and east-central Equatorial Pacific. For the past year and a half, near-neutral conditions have prevailed in the Pacific, meaning that neither an El Niño nor it's opposite, a La Niña, has been present. But as the video above shows, westerly winds have been picking up in parts of the western Pacific Ocean region, something that could signal the birth of El Niño. When neutral conditions are present in the Pacific, trade winds blow from east to west in the equatorial region. This tends to enhance upwelling of cold, deep water off the coast South America. These chilly waters spread toward the west, moderating sea surface temperatures. Meanwhile, strong trade winds corral warm surface waters on the western side of the ocean. But when anomalous westerly winds start to kick up north of New Guinea, things can begin to change by helping to weaken the trade winds and thereby set the stage for warm water to spread toward the South American side of the Pacific. Starting in January, and continuing into February and March, westerly winds have indeed begun to kick up. And earlier this month, a tropical storm helped enhance this pattern. And something else seems to be happening too.

Kelvin-wave.gif

A cross section showing temperatures in the equatorial Pacific Ocean at depth. Water that's up to 11 degrees F warmer than normal is moving toward the eastern Pacific at a depth about 160 meters. (Source: NOAA Climate Prediction Center) Right now, the surface waters of the equatorial Pacific Ocean are, overall, neither anomalously warm or cold. But at about 160 meters (525 feet) down, abnormally warm water is spreading towards the east in a phenomenon known as a Kelvin wave. You can see it in the graphic above. This is a cross-section of the Pacific Ocean down to 300 meters (almost a thousand feet). The numbers on the bottom (the x-axis) show degrees of longitude; 180 is the dateline, which is in the middle of the Pacific (to the west of Hawaii). Papua New Guinea is near 150E. The western coast of South America, including Ecuador and Peru, is near 80W. Those yellow, orange and red colors show the Kelvin wave, with water temperatures that are considerably warmer than normal. At his blog, Jeff Masters, chief meteorologist for Wunderground.com, connects the dots this way: "If unusually strong westerly winds continue over the equatorial Western Pacific during March and April, this Kelvin wave has the potential to trigger a strong El Niño event over the Eastern Pacific later this year." That said, using these changes in wind patterns and deep ocean temperatures in the spring to forecast an El Niño in the summer or fall is fraught with uncertainty. Thus, NOAA will go no further than saying there's a 50/50 chance of it happening. Klaus Wolter, a researcher at NOAA's Earth Systems Research Laboratory, believes the odds may be a little greater. Wolter independently uses a method to assess ENSO conditions known as the Multivariate ENSO Index, or MEI. And on Friday, he published an update on what it suggests is in store. His conclusion? "Compared to last month, the odds have increased further to make an El Niño likely in 2014." Wolter notes that compared to the official NOAA forecast, he is "even more 'bullish' on El Niño development in 2014, but that is a minor disagreement." If the Pacific Ocean does give birth to El Niño later this year, the beleaguered residents of Canada and the Upper Midwest of the United States might be spared a repeat next year of this winter's brutal polar conditions. That's because El Niño typically brings warmer than average temperatures to these areas.

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