El Niño, La Niña

by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station

I have the good fortune to be able to travel around the country and visit other field stations for an annual Organization of Biological Field Station conference where directors from all over exchange science, outreach, education, and management advice (www.obfs.org).  This is usually the highlight of my year.  This week I have been at two facilities on the West coast in California, the Bodega Bay Marine Lab north of San Francisco and Jasper Ridge Biological Station near Stanford. The dunes and vegation of Bodega Bay are simliar to our own; but the even more intense fog (really), warmer winters, and much higher organic content in the soil greatly changes the variety of plants and animals that live there (http://nrs.ucop.edu/reserves/bodega/bodega.htm). Our dune plants range from beach plum, rosa rugusa (introduced) and seaside heather to American beach grass and beach pea, salt tolerant plants that love sandy soil and don't need much in the way of organic matter to survive. Bodega Bay's dunes are covered with much different plants, like many types of lupine (yellow bush lupine, miniature lupine, sky lupine, chick lupine, lupine of the day, you get the point), coast tarweed, coyote mint, tidy tips, many others that sound like they came out of a Hogwart's class and sadly, much more invasive plants than we have (e.g., European beach grass and ice plants deliberately planted for erosion control). We do have some of the same plants like yarrow, sea lavendar, and cow parsnip. We have American oystercatchers, they have black oystercatchers. We have gray seals with the occasional harbor seal; they have harbor seals and sea lions. We have feral cats, they have mountain lions, although I've heard our cats are pretty fierce.

More often then not; unusual swings in temperature and a higher frequency of storms, hurricanes, and drought makes people think about climate change and the weather. As stewards of buildings in remote locations, field station and marine lab directors tend to trade horror stories of snow, wind, flooding, and fires.  As scientists do when we get together (less nerdy than you think), we start comparing notes on what we call major forcing factors on weather and climate like El Niño and La Niña (okay, maybe that's nerdy). To refresh our memories, we can go to the National Oceanic and Atmospheric Administration website for the latest news on this pendulum of warm and cold water. El Niño is characterized by unusually warm ocean temperatures in the Equatorial Pacific, as opposed to La Niña, which is characterized by unusually cold ocean temperatures in the Equatorial Pacific. El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe.

In normal, non-El Niño conditions, the trade winds blow towards the west across the tropical Pacific. These winds pile up warm surface water in the west Pacific, so that the sea surface is about 1/2 meter  higher at Indonesia than at Ecuador. Normally the sea surface temperature is about 8 degrees Celsius   higher in the west, with cool temperatures off South America, due to an upwelling of cold water from deeper levels. This cold water is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries.

So both El Niño and La Niña are abnormal ocean temperatures in the eastern Pacific Ocean, off the coast of South America. El Niños, wherein the ocean temperature rises at least 0.5 degree Celsius above normal, occur every two to seven years. An El Niño may or may not be followed by a La Niña, which is basically El Niño’s opposite.  An El Niño ended in the spring of 2005; the last significant La Niña was in the fall of 2000. One half a degree Celsius might not sound like much, but that is enough to disrupt upwelling, increase evaporation, or supply extra fuel to hurricane force winds. Scientists disagree about the cause for La Niña and El Niño; and they even disagree on which one we are in sometimes, which suprised me at the conference.

El Niño is translated to the "the Christ child," so named because of its frequent late December appearance. Once thought to affect only a narrow strip of water off Peru, it is now recognized as a large-scale oceanic warming that affects most of the tropical Pacific. The meteorological effects related to El Niño and its counterpart, La Niña extend throughout the Pacific Rim to eastern Africa and beyond. You might remember when I wrote about tidal anomalies along the East coast back in 2009 that some scientists thought there could be a link to El Niño. El Niño is normally accompanied by a change in atmospheric circulation called the Southern Oscillation. Together, the ENSO (El Niño-Southern Oscillation) phenomenon is one of the main sources of interannual variability in weather and climate around the world. Since recognizing some 25 years ago that the oceanic and atmospheric parts of ENSO are strongly linked, scientists have moved steadily toward a deeper understanding of ENSO. Climate forecasters have taken the first steps toward predicting the onset of El Niño and La Niña events months in advance. Still, much remains to be learned about these children of the tropics.

The best way to tell them apart is from the Spanish derivation, El niño means “little boy”; la niña, “little girl.” Knowing that, all you have to remember is that little boys are (only for the purpose of this analogy) the hotheads. El Niño is a disruption of the ocean-atmosphere system in the Tropical Pacific having important consequences for weather and climate around the globe. Our local weather and climate and Bodega Bay's are effected in some extent by La Niña and El Niño as are most areas around the globe. This web site from NOAA, www.elnino.noaa.gov,  has the most recent sea surface water teperatures across all the worlds oceans. When you look at these global animations you can start to see how the fluid connection works between air and water. Remember that El Niño is characterized by unusually warm temperatures and La Niña by unusually cool temperatures in the equatorial Pacific. Anomalies represent deviations from normal temperature values, with unusually warm temperatures shown in red and unusually cold anomalies shown in blue. Currently the status is (according to NOAA site) “ La Niña conditions have returned and are expected to gradually strengthen and continue into the Northern Hemisphere winter 2011-12. During September-November 2011, there is evidence that La Niña favors an increased chance of above-average temperatures across the mid-section of the country, and an increased chance of above-average precipitation across the Pacific Northwest.”

So why should we care about a 5 degree temperature change in an ocean far away? Well, in 1997 and 1998 we had a El Niño/La Niña back-to-back bout that effected climate across the world, not the least of which was disastrous rainfall from Poland to Chile and drought in Indonesia. For example, El Niño is known to intensify winter storms for residents of the West Coast, Gulf states, and southeast United States. El Niño also dampens Atlantic hurricane formation and can increase the number of Pacific hurricanes. Basically these swings in oscillation act are like an out of control swing on a swing set; what was once a nice back-and-forth starts to get dangerous and turbulent. And expensive for coastal towns! El Niño alone is believed responsible for more than 2,000 deaths from flooding, mud slides, and storms. It’s also estimated to have cost $33 billion in property damage—more than Hurricane Katrina. Fisheries that are supplied by upwelling along the Chilean coast suffer during El Niño events as the nutrients rich food from the depths does not come up to form the base of the food chain. Recent research has shown that the El Niño that occurred in the 1918/1919 caused a severe drought in India that compounded and possibly increased mortality from the Flu Epidemic (http://www.elnino.noaa.gov/pandemic_1918_1919.html ). Back then there were not a lot of weather monitoring stations around the globe nor were there the backbone of instrumented ocean buoys that scientists (many associated with field stations) have been installing and maintaining around the world.

This brings us back locally as I spend the winter updating three temperature buoys I hope to place out into the harbor next year. In this case, the more data you can accumulate and check, the safer you can make the world or at least you can be prepared.