Natural Variation of Sr Isotopes in coral Porites Collected from Nanwan Bay, Southern Tip of Taiwan
Date Issued
2010
Date
2010
Author(s)
Liu, Yi-Wei
Abstract
Monthly resolution 87Sr/86Sr records of living coral Porites heads, collected in the Nanwan Bay, southernmost Taiwan (21o55’N, 120o47’E), were analyzed by a MC-ICP-MS at the Department of Geosciences, National Taiwan University. For stable Sr isotopic analysis, a 84Sr/86Sr double spike method was applied on TIMS at Institute of Earth Sciences, SINICA. The data show no relationship between δ88/86Sr and seawater temperature. Between the time window of 1992 and 2002, 87Sr/86Sr ratios show good relationship with the ENSO index. No relationship is found between 87Sr/86Sr and climate proxy data, both Sr/Ca and δ18O, which suggests that the effect of temperature and fresh water input are negligible to the observed fluctuations of 87Sr/86Sr in these corals. By checking 87Sr/86Sr in Nanwan water, it shows that a simple two end-member mixing model cannot explain the observations. A profound magnitude of subsurface water upwelling with low 87Sr/86Sr should be included to contribute low Sr isotopic ratio in southern Taiwan. Compare to the Nino 3.4 index, the results show that during strong El Nino years such like 1994-1995 and 1998, 87Sr/86Sr ratios were lower than the average. On the contrary, in 1999 and 2000 La Nina years, 87Sr/86Sr values were higher than the others. This suggests that the variation of radiogenic Sr isotopes probably related to ENSO variability (Fig. 4.2). ENSO related Luzon Strait transport and the corresponding remix of surface and subsurface seawater were found (Hsu and Liu, 2004; Qu et al., 2004), and these events in the past may be traced by 87Sr/86Sr in corals.
Subjects
Coral
Sr isotopes
Nanwan Bay
Type
thesis
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