This learning activity involving the identification of El Niño events in X-radiographs of a X-sections of coral core from Vanuatu, and the development of a predictive model of ENSO events based on the data. Source: T. M. Quinn, et al, 1999, New Caledonia Coral Multicentury Stable Isotope Data,IGBP PAGES/World Data Center-A for Paleoclimatology Data Contribution Series #1999-003. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. Time Frame - 30 minutes Materials
Advance Preparation Presenter/teacher will explain how core was collected (slides, examples of tools, cores) and review how reef-building corals create an exoskeleton. Procedure
Formative AssessmentCheck to see if participants were able to (1) calculate the length of time that the core represents by counting the growth bands in the coral; (2) identify El Nino events in X-radiograph of X-section ; and (3) develop a rough predictive model of ENSO events based on the data. Learning Experience 2. Coral as seawater thermometers Time Frame - 11/2 hours Materials
*Nome Climatologies (Word) *40 years (1953 - 1992) of monthly delta 18O and 13C data samples from a New Caledonoia coral core (Excel) *40 years (1953 - 1992) of corresponding monthly sea surface temperatures *40 years (1953 - 1992) of corresponding monthly sea surface temperatures, air temperatures, and ocean salinities (Excel file) Advanced PreparationReview basic atmospheric circulation, the system of ocean currents and thermohaline circulation. Explore the role of the WPWP. Review the basic chemistry of seawater. Review the biogeochemical process used by corals to create their exoskeletons. Review oxygen isotopes in corals. In the process of building their skeletons, corals secrete CaCO3 using H20, HCO3- from the surrounding ocean and the oxygen released by the zooxanthellae that live symbiotically with them during photosynthesis. The ratio 18O/16O in specific growth bands in corals can be correlated with the temperature of the ocean corresponding to that growth band. Procedure
Formative Assessment The presenter will provide the conclusions of Taylor and colleagues. The presenter will also reveal new questions raised by the data set. Summative Assessment Probably everybody knows about El Niño, and they know that it can affect the weather in a given year. However, most people do not really understand what El Niño is. Many people have heard all different sorts of explanations and have formed somewhat of an idea, but that idea is usually rather distorted. Thanks to explosive media coverage of El Niño during the 1997-1998 season, the general public has become rather panicked. Lately, any mention of El Niño initiates bitter discussion on the subject, and almost every natural phenomenon (especially destructive ones) gets blamed on El Niño. However, this is just not the case. True, many different weather events occur simultaneously with most El Niño years, but El Niño does not dominate the earth’s climate. Unfortunately, most people do not realize this, and ignorance on the subject is widespread. Therefore, the title of “Ugly Duckling...” can be applied because El Niño is usually deemed “bad” by those who do not understand it. Divide participants into cooperative/collaborative groups and assign each group one of the following questions to discuss. Note: If participants do no have enough background information to discuss the questions, you might provide each group with the question and explanation written below. Then have each group give a short two minute presentation to summarize the group’s discussion. Give groups chart paper and markers and encouage groups to draw illustrations and diagrams to illustrate their explanation. What is El Niño? Originally, the term “El Niño” was used by the local residents along the coasts of Ecuador and Peru to describe the annual weak, warm ocean countercurrent that flows southward along the Pacific coast of South America. Usually, the ocean current flowing through the region is a cold one (see diagram above), however, each year this “El Niño” current is noticed around December, and normally lasts only a few weeks. Today, scientists around the world use the term “El Niño” to describe an exceptionally strong, warm ocean countercurrent along the same region that lasts up to 24 months. This phenomenon has been studied for approximately the last 50 years, and it occurs irregularly every 3 to 7 years. Therefore, the modern working definition of “El Niño” is: an anomalous warming of surface waters in the eastern equatorial Pacific Ocean. Why is it called El Niño? Since the annual phenomenon that was originally named El Niño occurs around December each year, the local residents of Ecuador and Peru named it for the Christ child. In Spanish, “El Niño” actually translates--"the child.” What causes El Niño? Another phenomenon that is associated with El Niño is what is known as the Southern Oscillation. Usually, the barometric (air) pressure is is much higher in the southeastern Pacific than in the western Pacific (centered over Indonesia and northern Australia). This situation sets up a steep pressure gradient (slope) that results in strong winds flowing west across the Pacific. These strong winds help keep warm waters in the west from flowing to the colder waters of the east. However, during the Southern Oscillation, the difference in pressures lessens and sometimes the locations of the high and low pressure centers even reverse. When this happens, the pressure gradient is reversed, and the winds are blowing the warmer waters towards the east. El Niño is the name for the warmer waters in the east. It is not clear at the present time what causes the Southern Oscillation. It is obvious that El Niño and the Southern Oscillation (ENSO) are closely coupled, but what exactly initiates the event is unknown. El Niño has been documented since 1726, but the relationship with the Southern Oscillation was only noticed in the 1960’s. In the past twenty years, several research projects have been funded to find out more about ENSO, and a thorough understanding is certainly probable in the near future.
How does El Niño affect the United States? During past El Niño events, the United States has not been spared losses. The typical changes in weather in the U.S. due to El Niño include droughts in the Southwest and flooding in the West and Southeast. During the 1982-1983 El Niño event (the strongest on record), the U.S. experienced one of the warmest winters followed by one of the wettest springs ever. Extreme amounts of precipitation (rain and snow) caused massive landslides, floods, and erosion in the west, and the southeast was also flooded by abnormally heavy rains. The results of El Niño-related weather usually causes concern in the U.S. because damage costs rise quickly. However, the weather events are not always extreme, but merely different. All regions learn to adapt and live comfortably under certain climatic circumstances. When those circumstances are altered, the way of life in that region will certainly be affected--usually economically.
How does El Niño affect other countries? Some typical affects of El Niño in countries other than the United States are droughts in Indonesia, Australia, Mexico, and southeast Africa. Other areas, such as western and central South America receive unusually high amounts of precipitation. All of these effects are not necessarily bad. For example, more rains in some of the more inland regions of Ecuador and Peru help produce higher yields for pastures and cotton fields. However, many effects can be disastrous, and during the 1982-1983 El Niño event, over 1500 human deaths and nearly $9 billion in damages were attributed to El Niño. The effects that El Niño and the Southern Oscillation have on the rest of the world is known as “teleconnections.” Unfortunately, scientists do not know exactly why El Niño is accompanied by these weather changes. Many theories have been formed, but more research is still required to create a firm explanation.
How often does El Niño occur? At the present time, scientists do not know what triggers an El Niño event, therefore it is hard to pinpoint when it will occur. However, historical averages show that we experience El Niño every 3 to 7 years.
When has El Niño occurred before? Most certainly El Niño has been occurring periodically for centuries, and it has even been documented as early as 1726. However, scientists have only been actively studying El Niño for less than fifty years, so previous records are rather slim. Here is a list of El Niño years that have been scientifically documented in recent history: 1951-1952 1957-1958 1965-1966 1968-1969 1972-1973 1977-1978 1982-1983 1991-1992 1997-1998 EXTENSIONS 1. Global heat balance and mechanisms for distributing heat globally.
2. Heat exchange across the air/sea interface. In a normal year, the heat that accumulates in the WPWM is transferred to the atmosphere across from the surface of the ocean resulting in layers of different temperatures and densities in both the ocean and atmosphere. Learning activity (1) using Radon-222 (or SF6) data to determine gas exchange across the air-water interface, and (2) involving the calculation of the quantify of heat transferred to the atmosphere. 3. The CERES S’COOL Project activities (http://asd-www.larc.nasa.gov/SCOOL/) |