OCEAN WATCH departs from Los Sueños, Costa Rica today. We will be sailing into what is left of the 2009-2010 El Niño event which is considered to be one of the most intense of the past decade. We have new instruments to help us define and record the structure of the surface waters through which we will pass. The coastal waters off of the west coast of the Americas, and the atmospheric boundary above, are extremely important for local economies and are crucial for our understanding of climate changes. In this and following reports we will endeavor to explain some of the complexity of ocean and atmospheric circulations as they relate to our observations.
Peruvian Fisheries
One of the world’s richest fisheries is off the coast of Peru. In most years winds from the southeast, in a process called “upwelling,” push warm surface water away from the coast. In its place, upwelling brings cold water rich in nutrients to the surface. (See the left map of sea surface temperature below.) The nutrients provide nourishment for the microscopic plants know as plankton. Plankton normally provide food for a vast community of anchovies and other fish. The fish in turn supply food for seabirds. Not only is the fish catch economically important, the harvesting of bird excrement (guano) provides a supply of valuable fertilizer.
Every few years, typically five years, the pattern of air circulation over the equatorial Pacific changes in a way that shuts down the coastal upwelling. When the upwelling stops, surface waters warm considerably from less than 60 to over 80 degrees F (15-35 degC). Everything that depends on the overturning suffers catastrophic decline: nutrient concentration declines which reduces plankton productivity followed by the collapse of the fishery. Birds die by the thousands. The natives of Peru knew this regular event and the named it “El Niño” for the Christ child.
| Normal Years | El Niño 2010 |
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| This map shows the sea surface temperature (SST) over the world’s oceans for a normal year. The dashed boxes show regions of upwelling where overturning of the surface water brings up nutrients. The deeper water is colder and thus one sees that the coastal water SST is much cooler than that offshore. The fertile waters drive huge local fisheries. | This map shows global SST for February 2010, an El Niño year. Notice the waters off Peru are now warm and the upwelling region has moved south and offshore. The waters off of Costa Rica are quite warm too. The upwelling area off of North America is still active if not broader. This SST map is for February 2010 and the El Niño event is coming to an end. |
Some biologists fear that the overfishing of the anchoveta by humans, plus the eating of anchovies by large fish and seabirds, combined with the injurious effects of an intense El Niño episode, like the one in 1997-98, could reduce the anchoveta stock to such critically low numbers that recovery could be difficult. The 1972-73 El Niño caused a serious drop in the fish catch which took years to recover. Since then, the Peruvian government has worked hard to regulate fishing in their territorial waters. Fortunately they have been successful, and the fishery has recovered from even severe El Niños like the one in 1988-1989.
El Niño: a local effect of a global event
If we would please society we must be prepared to be taught many things we already know by people who do not know them!
Nicolas Chamfort
I want to explain this very interesting physical process, but how? The subject is so well researched and so well explained in thousands of articles, books, and web pages that I cannot imagine how I could contribute to that infinitude of knowledge available to people of every degree of expertise. Nevertheless, with Chamfort’s advice in mind I shall forge ahead.
By now most people have heard of El Niño, if only to know the name refers to some kinds of abnormal weather. The definition of “abnormal” varies widely with geography, though. For people who live in Indonesia, Australia, or southeastern Africa, El Niño can mean severe droughts and deadly forest fires. Ecuadorians, Peruvians, or Californians, on the other hand, associate it with lashing rainstorms that can trigger devastating floods and mudslides. Severe El Niño events have resulted in a few thousand deaths worldwide, left thousands of people homeless, and caused billions of dollars in damage. Before the winter of 2010 residents on the northeastern seaboard of the United States credited El Niño with milder-than-normal winters (and lower heating bills) and relatively benign hurricane seasons. After the past severe winter in the Northeast US, all bets are off and one can say simply that weather is chaotic and extreme.
If you ever wanted to have an appreciation of how beautifully interconnected Nature can be, taking into consideration all the workings of weather and climate, as well as the responses of the biological sphere and concomitant chemistry, take a moment to consider the intricacies of El Niño. Back in the 70’s, before we had global warming to blame, just about any extreme weather event, drought in California, floods in the midwest, heavy rain in California, intense hurricanes, or anything else you might mention was blamed on El Niño.
On 10 April, 2010 the headlines were different: “Landslides and floods kill 200 people as Rio de Janeiro drowns under ELEVEN inches of rain in just 24 hours.” The death toll following the heaviest rains in Rio de Janeiro’s history was set to soar above 200 after a new mudslide hit neighbouring slums. The latest landslide surged into a rain-sodden hillside shanty town in Rio’s neighbouring city of Niteroi, engulfing at least 40 homes in a cascade of mud. The ground gave way in steep hillside slums, cutting red-brown paths of destruction through shantytowns. Heavy flooding in some places and terrible droughts in others result from a readjustment in circulation patterns caused by the El Niño and associated events.
Note that the disruptions from the El Niño occur every 4-6 years and last 1-2 years. These events are superimposed on the global climate change which is on a scale of centuries.
But El Niño is a local manifestation of a global change in weather patterns. As described above, the name was coined in the late 1800s by fishermen along the coast of Peru. Today, the term no longer refers to the local seasonal current shift but to part of a phenomenon known as El Niño-Southern Oscillation (ENSO), a continual but irregular cycle of shifts in ocean and atmospheric conditions that affects the entire world. El Niño has come to refer to the more pronounced weather effects associated with anomalously warm sea surface temperatures interacting with the air above it in the eastern and central Pacific Ocean. Its counterpart–effects associated with colder-than-usual sea surface temperatures in the region–was labeled “La Niña” (or “little girl”) as recently as 1985.
The OCEAN WATCH crew certainly noticed the very warm water as they sailed along the Peruvian coast to the Galápagos and on to Costa Rica. We expected the cooler waters and upwelling, but water temperatures were well above 28 degC (82 degF) which made cabin conditions very unpleasant. The dormant fishing fleets lined the docks and the ports were quiet.
The shift from El Niño conditions to La Niña and back again takes about four years. Understanding this irregular oscillation and its consequences for global climate has become possible only in recent decades as scientists began to unravel the intricate relationship between ocean and atmosphere. Although meteorologists have long been forecasting daily weather based on atmospheric measurements taken around the world, they had relatively little information about conditions in many parts of the world’s oceans until the advent of arrays of fixed, unmanned midocean buoys in the Pacific Ocean and orbiting satellites.
But technological advances were not the only key to understanding. Atmospheric and oceanographic researchers, after years of independent inquiry into the basic workings of air and sea, have at last joined forces. An elegant synthesis of these two fields of research now enables climatologists and oceanographers to construct theoretical models to simulate and predict the broad climate changes associated with ENSO. For example, scientists can now warn vulnerable populations of an impending El Niño event several months in advance, providing precious time in which to take steps to mitigate its worst effects. Invaluable as this prediction of El Niño is, it is just the first step toward the much longer-term goal of providing the climatic counterpart to the daily weather prediction that we have come to take for granted.
Future reports
Today we sail from Los Sueños and head north towards Puerto Vallarta. We have two new pieces of oceanographic instrumentation with us which we will discuss in future reports. The premier manufacturer of oceanographic instrumentation, Sea-Bird Electronics, in Bellevue Washington, has provided us with a thermosalinograph (TSG) which will provide a continuous record of surface temperature and salinity. The TSG is run with the SeaKeeper instrument and will provide validation and cross reference to the SeaKeeper measurements. Secondly we have a Sea-Bird conductivity-temperature-depth (CTD) instrument which we will lower from the boat to get a profile of the temperature, salinity, and pH through the surface waters. We will be able to report on our findings as we progress. As a scientist, I must say how excited I am to have these instruments in this very important El Niño event.
Michael Reynolds, Ph.D.
April 10, 2010
