A True Representation of El Nino (Final)

This discussion topic submitted by Elizabeth Bentley (not applicable) on 7/9/98.

I. History of El Nino
a. The cool waters off the coast of Peru (avg.21-26C) provide a
good environment for the anchoveta fish to thrive.

b. "Guano" birds, who make a home of the Peruvian coast, produce an
excretion high in phosphorous and nitrogen. This excretion was
exported as a fertilizer and contributed to Peru's economy.

c. El Nino, a warming of the waters off the coast of Peru, altered
the habitat of the anchoveta and caused the fish to disperse.
The guano birds are unable to find food and die. The Peru
economy suffers as a result of the dying bird.

II. Eastern Tropical Pacific vs. Western Tropical Pacific
a. Conditions in the Eastern tropics are usually cool and dry with
water temperatures between 21-26C.
1) Coastal upwelling, a drawing up of cool, deep water to the
surface, occurs as a result of TRADE WINDS (E to W) and the
rotation of the earth.

b. Conditions in the Western tropics are typiclly warm and wet
with the average temperature at 29C. The warm water heats up
the above atmosphere and creates the conditions for
precipitation to form.

c. During an El Nino year the trade winds reverse direction and
flow from West to East. This reversal moves the warm waters of
the Western tropics eastward and exposes the cooler, deeper
water in the West...bringing the THERMOCLINE closer to the
surface in West.
1) Drought conditions in Australia/Indonesia (Western Pacific)
2) Flooding occurs in Peru (Eastern Pacific)

III. Southern Oscillation
a. This oscillation involves a see-saw like change in sea level
pressure across the Pacific Basin.

b. Two areas, Darwin, Australia and the island of Tahiti, have an
inverse relationship to one another in the area of sea level
pressure. When one area has high pressure, the other area has
low pressure.

c. Scientists use the SOUTHERN OSCILLATION INDEX as a tool for
determining an El Nino year. The pressure in Darwin is
subtracted from the pressure in Tahiti. A negative number
indicates an El Nino year.

IV. Positive Impacts
a. The coastal deserts of Peru experience increased rainfall and
increased vegetation. Settlers in the area can raise cattle
and sheep and make a living.

b. The Western coast of South America experiences increased
sardine, mackeral, and scallop populations, therefore boosting
the economy.

c. The Atlantic enjoys a decreased number of tropical storms.

V. Why the Emphasis on Negative Impact?
a. Increasing coastal populations in the U.S. over the past ten
years results in extensive damage from flooding and mudslides.
This is a HUMAN decision to move to coastal areas.

b. Additional global climatic factors are occurring and feeding
into El Nino's destuctive reputation.

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