ABSTRACT
This study presents a 271-year (1726-1997) subseasonal oxygen and
carbon isotopes (d18O and d13C) records from a coral colony of
Porites lobata at Rarotonga (21.5°S, 159.5°W) in the
southwest subtropical Pacific. A new method is introduced whereby
the effects of sea surface temperature (SST) can be separated from
those of seawater d18O composition (d18Osw) on coral d18O by using
the coupled coral Sr/Ca and d18O. The reconstructed d18Osw at
Rarotonga using this method shows that it contributes
significantly to the annual changes of coral d18O for the period
1726-1997. While changes of d18Osw account for ~39% of the total
coral d18O variation, changes of SST account for ~61%. The
reconstructed d18Osw also shows a positive linear correlation with
a satellite-based estimated salinity for the period 1980-1997
(r=0.72). This linear correlation between reconstructed d18Osw and
salinity makes it possible to use the reconstructed d18Osw to
estimate the past interannual and decadal salinity changes in this
region.
Applying a similar method to coral d13C, the effects of kinetic
and metabolic activity on coral d13C were also quantitatively
separated. The results show that the variation of coral d13C
appears to be mainly caused by variation of metabolic activity
rather than that of kinetic activity in both tropical and
subtropical regions. For the tropical regions, d13C variation in
corals is predominantly influenced by changes of metabolic
activity (~90%), while for subtropical regions, approximately
70-75% of the total variation of coral d13C is due to the effects
of metabolic activity.
The interannual and interdecadal variability in coral d18O at
Rarotonga for the period 1726-1997 was also examined. The results
suggest that although Rarotonga is located outside of the center
of action of ENSO, it is generally sensitive to ENSO variability
in this region. In addition, the decadal variability (~12 yr) was
further differentiated from the interdecadal-scale variability
(~32 yr) for the period 1726-1997 at Rarotonga. Based on the
analysis of both tropical and subtropical coral data and
comparisons with the Nino3.4 SST index and PDO index, it was
hypothesized that the decadal and interdecadal variability might
result from separate forcing mechanisms.
Ren L., 2002. A study of a multi-century coral stable isotope
record from Rarotonga, southwest subtropical Pacific, for the
period 1726-1997.
Unpublished PhD dissertation, State University of New York at
Albany. 184pp., +viii
University at Albany Science Library call number: SCIENCE
MIC Film QC 869 Z899 2002 R46
Copies of this PhD dissertation can be ordered
from Proquest UMI
Front matter (title,
table of contents, abstract, acknowledgements) - 0.2MB pdf
file
Figure pages in dissertation
(colour
and greyscale figures, with captions): - 12.7MB pdf file
Appendices: I - Coral δ18O
and δ13C in cores B and C from Rarotonga for the period 1726-1997
II - Coral δ18O and δ13C in core 3R from
Rarotonga for the period 1926-2000
(Appendices
I and II as digital pdf tables) - 0.25MB pdf file
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