期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 75, 期 14, 页码 3930-3944出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2011.04.017
关键词
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资金
- Australian Research Council [DP0664313, DP1092945]
- ANSTO
- Australian Institute of Nuclear Science and Engineering Research (AINSE)
- Australian Research Council [DP0664313, DP1092945] Funding Source: Australian Research Council
Understanding the influence of climatic and non-climatic factors on geochemical signals in corals is critical for assessing coral-derived records of tropical climate variability. Porites microatolls form large, disk-shaped colonies constrained in their upward growth by exposure at or close to mean spring low water level, and occur on Indo-Pacific reefs. Microatolls appear suitable for paleoclimate reconstruction, however the systematics of the microatoll chemistry-climate relationship are yet to be characterized. In this study, the delta O-18 signal in Porites microatolls from well-flushed reef flats on Kiritimati (Christmas) Island, central Pacific was investigated for intra-coral (growth aspect and extension rate effects) and between-coral effects, and to explore the climate signal contained within their skeletons. Samples for delta O-18 analysis were taken from six individual transects from different positions within Porites microatoll XM22. The results show that: (1) the average standard deviation for the mean delta O-18 values of transects that represent the same time periods is 0.03 parts per thousand, and is within measurement error for a single analysis (0.04 parts per thousand); (2) the average standard deviation for time-equivalent, near-monthly samples along the transects within the same microatoll is 0.07 parts per thousand and; (3) comparison of the average delta O-18 values of records for different microatolls from across Kiritimati Island show only a small between-coral differences of 0.04 parts per thousand and 0.11 parts per thousand for different time periods. These differences in mean delta O-18 are within the range for intra-and inter-colony differences in seasonal and interannual delta O-18 reported for dome-shaped Porites. Based on these results, a stacked microatoll delta O-18 record was constructed for the period 1978-2007 for comparison with published coral delta O-18 records for nearby dome-shaped Porites. There is a systematic offset between the two types of records, which is probably due to variations in delta O-18 seawater across Kiritimati Island. Despite the offset, all records show similar amplitudes for the seasonal-cycle of delta O-18, and there is a strong correlation (r = -0.71) between microatoll delta O-18 and local sea surface temperature (SST). The delta O-18-SST slope relationship for microatolls is -0.15 parts per thousand/degrees C, very similar to that reported for fast-growing domed corals (-0.18 parts per thousand to -0.22 parts per thousand/degrees C). Statistical analysis of the stacked microatoll delta O-18 record shows that it is correlated with both local and large-scale climate variables (primarily SST) at semiannual, annual and interannual timescales. Our results show that the signal reproducibility and fidelity of skeletal delta O-18 in coral microatolls is comparable to that observed for more conventional coral growth forms. Longer-lived, and fossil, Porites microatolls, where they have grown in suitably flushed environments, are likely to contain delta O-18 signals that can significantly extend instrumental records of tropical climate variability. Crown copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
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