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| Titel |
Coral isotopic records during the medieval period from Ishigaki Island, northwestern Pacific |
| VerfasserIn |
Maki Morimoto, Osamu Abe |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078322
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| Zusammenfassung |
| Proxy-based paleoclimate reconstructions in high time-resolution and modeling studies have
been greatly advanced in recent years to understand global temperature history over the past
1000 years. However, most proxy data for these reconstructions are from terrestrial sources
such as tree-rings, speleothems, etc., and very few marine records in annual resolution have
been obtained over 500 years. This is considered to be one of reasons for large
uncertainties of global scale climatic reconstructions. Marine sediments can provide
long consecutive records from several thousands of years to several million years.
However, their time-resolutions of several tens to several thousands of years are
insufficient for reconstructing decadal to centennial climate variabilities. Coral
skeletal proxies, such as oxygen isotope ratios (δ18O) and Sr/Ca, have been used to
reconstruct tropical and subtropical sea surface paleoenvironment in much higher
time-resolution of weeks to months, which could provide comparable results with tree-ring
records.
The Northwestern Pacific is one of regions with sparse long paleoclimate records in high
time-resolution for the last 1000 years. We collected a medieval fossil coral (Porites sp.) with
a height of more than 5 m from a fringing reef of the southern coast of the Ishigaki Island,
southern Japan, where the East Asian monsoon is predominant. Using combined annual age
determination by annual band analysis and high resolution isotope measurements,
yearly δ18O was obtained spanning 300 years of about 1000 years ago (1535+-35
~ 1260+-80 14C age (ca. cal AD 850 ~ 1150)). This period corresponds to the
beginning of the Medieval Warm Period, recently more commonly referred to as the
Medieval Climate Anomaly (Stine, 1994), and it also is marked by a tendency for La
Niña-like conditions in the tropical Pacific (Mann et al., 2009). Here we discuss
about the transition to the warm period of the northwestern Pacific and its degree by
comparing with other regions’ and large-scale reconstructed temperature variations. |
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