Abstract
As interest in global climate change increases, so does the need for
better and more extensive climate proxies. The central equatorial
Pacific has been established as the region with the largest
ENSO-related sea surface temperature (SST) and precipitation (PPT)
anomalies, which are known to impact global interannual climate
variability. To date, the coral genus Porites has been most commonly
utilized for coral-based paleo-reconstructions of ENSO and lower
frequency phenomena. However, due to questions of biological
artifacts in coral, to more fully understand coral-based
reconstruction, different coral genera need to be analyzed.
In this study, oxygen (δ18O) and carbon (δ13C) isotopic time series as
well as Sr/Ca time series, were generated from a colony of the massive
hermatypic coral Montipora venosa,
(a
genus not previously studied) from an ENSO sensitive site.
This coral core was recovered from Fanning Island (3º 52’N,
159º 20’W) in the central equatorial Pacific, located in the heart
of the important Niño 3.4 region for monitoring ENSO.
Oxygen isotopic data from Montipora
venosa core (FI4) is compared to previously unpublished δ18O
data from a Porites sp. core
(FI5) taken at the same location. Even though core FI4 M. venosa is the shorter core
(662mm), it spans 111yr (1997-1887), while the longer FI5 Porites core (1260mm) spans only 75
yr (1997-1922).
Core FI5 Porites contains a
deviation of undetermined cause towards increased δ18O values between
1950 and 1951, which is not recorded in core FI4 Montipora venosa. This
deviation is not found among other central equatorial Pacific Porites records and thus supports
the need for a multi-core replication strategy.
There has been a suggestion by Cane et al. (1997) that the pattern of
20th century SST change across the Pacific may be due to an increase in
the west to east temperature gradient. However, comparison of the
M. venosa core FI4 δ18O time
series with δ18O time series from Maiana (1ºN, 173ºE) and
Urvina Bay (0º 24.5’S, 91º 14’W) indicates there has been no
change in SST gradient across the Pacific during the studied time
period (1997-1887), assuming that δ18O is primarily affected by
temperature at all these sites.
Coral data from several locations throughout the Pacific Ocean show a
shift in 1976 towards lighter δ18O values, which is often interpreted
as a trend towards warmer SSTs. However, it is not clear how much
of this trend is real and how much might be attributable to biological
effects. The results of this study indicate that the magnitude of
the shift varies not only by location, but also by coral genus.
Again, this substantiates the need for a replication strategy.
Stolorow, Alexa, 2006. Assessing the Paleoceanographic Potential of
the coral Montipora venosa at Fanning Atoll, Central Equatorial
Pacific.
Unpublished MSc. thesis, State University of New York at
Albany. 104 pp., + x
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 40 Z899 2006 S76
MS thesis pdf (2 MB)
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