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past feature
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Pacific Coral Signals
Climate Change
Coral extracted from a remote island in
the Pacific Ocean has enabled scientists
at the Scripps Institute of Oceanography
in San Diego to construct a new record of
climate conditions during the 20th
century.
The coral cores allow researchers to trace
sea surface conditions over a
112-year-period, and may hold implications
for long-range climate forecasting and
predictability.
Samples were drawn from a tiny Pacific
atoll called Palmyra by Kim Cobb and
Christopher Charles. Using mass
spectrometry, Cobb measured tiny
differences in the ratio of oxygen
isotopes in the coral cores. These
differences allowed Cobb to determine
precisely how the monthly sea water
temperatures changed, thus becoming a
detailed climate record for the tropical
Pacific.
"Several important implications arise from
these findings, including the possibility
that the observed global climate
variability on decadal time scales
reflects a 'teleconnected' response to
changing conditions in the central
tropical Pacific Ocean," said Kim Cobb, a
lead author of the study published in the
June 1 issue of Geophysical Research
Letters.
Climate scientists have developed models
that outline several scenarios for air-sea
interactions that operate on cycles
described by Cobb and Charles, known as
"decadal variability." However, proof from
the field, or instrumental records, have
been sparse. Prior to World War II,
significant gaps existed in critical
regions of the ocean, especially from the
vital tropics regions. Over two weeks,
Cobb and a small team used portable drills
to extract more than 70 samples from coral
heads above and below sea level.
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