Carbon and oxygen isotopic composition of a Guam coral and their relationships to environmental variables in the western Pacific

We examine the high-resolution (similar to32 samples/year) carbon and oxygen isotopic composition (delta(13)C(coral) and delta(18)O(coral)) in a coral core (Porites lobata) from Double Reef, Guam over the years 1980-2000. The delta(13)C(coral) shows clear seasonal variations with mean seasonal amplitude of 1.89parts per thousand, which roughly corresponds with seasonal variations in solar radiation. The seasonal amplitude of delta(18)O(coral) variations are small (0.23-0.57parts per thousand), but they are significantly correlated with sea surface temperature (SST) and salinity (SSS). The delta(18)O(coral) and SST are more strongly correlated during El Ni (n) over tildeo/Southern Oscillation (ENSO) warm phases (r=-0.8l,p<0.01) than during non-ENSO phases (r=-0.65,p<0.01) and ENSO cool phases (r=-0.48,p<0.01). These different relationships are due to differences in winter SST and in seawater delta(18)O (delta(18)O(sw)) during ENSO warm phases (<27 degreesC and higher values of delta(18)O(sw)) compared with cool phases (>28 degreesC and lower values of delta(18)O(sw)) at Guam. These differences in oceanic parameters result from movements of the Western Pacific Warm Pool (WPWP) during the different phases of ENSO. Anomalies in delta(18)O(sw), inferred from the delta(18)O(coral) and instrumental SST, are consistent with SSS anomalies for the years 1980-2000. These delta(18)O(sw) anomalies may reflect changes in SSS and evaporation-precipitation due to movements of the WTNNIP. This detailed analysis of a coral from Guam suggests that it may contain an excellent archive of past ENSO events. (C) 2004 Elsevier B.V. All rights reserved.