El Niño is a natural event that has been occurring for thousands of years, so Peruvians should expect its arrival. Unfortunately, no one knows exactly when the next El Niño will occur, how intense it will be, or how long it will last. We only know that the average occurrence is every 3-7 years and it lasts for an average of 1-2 years. Scientists are working to find ways to better predict when the next El Niño will come and how strong it will be. Buoys are set up along the equator of the central Pacific to take records of the sea surface temperatures (SSTs), wind speeds and barometric pressures. When the winds slow down an El Niño is on its way.
Scientists can also detect the past occurrences of El Niño by looking at the past sea-surface changes in corals. El Niño affects the growth and chemistry of the coral bands. Isotopes of oxygen locked in the coral skeleton record past water temperatures and can indicate an El Niño. The information recorded in the coral bands can tell us more about the frequency and duration of El Niños.
During the strongest ENSO of the century in 1982-83, the temperatures
in the western Pacific increased by up to 5 degrees Celsius. The stress
due to warmer than normal temperatures caused some of the coral polyps
to bleach. Although bleaching after El Niño is normal, the amount
of coral bleaching seems to be on the rise, and El Niño appears
now to be affecting areas that have not been affected in the recent past.
Photo Credits:
Sarah H. Dawson
NOAA Paleoclimatology Program
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