Senior Theses 2005
Kristen Mitchell (2005). Comparison of modern and fossil
coral climatology in the western Pacific warm pool
Faculty Advisor: Joel Thompson
Climate records from an ~ 8,000 year-old fossil coral from Tetepare, western Solomon Islands, are compared with those from modern corals from Rabaul, Papua New Guinea, to assess changes in mean climate state and climate variability in the Western Pacific Warm Pool (WPWP), a region that serves as a heat engine for earth's climate and as a major moisture source for earth's hydrological cycle. The WPWP also plays a central role in the EI Nino-Southern Oscillation (ENSO) climate phenomenon. A better understanding of the history of natural climate variability from this climatologically significant region may provide insight into future climate change scenarios in response to human activities. The fossil coral sample used in this study was judged to be pristine based on multiple criteria (e.g., mineralogic, petrographic and geochemical). The 16-year long, monthly resolved time series of variations in fossil coral and Sr/Ca all display a strong annual cycle and have mean values of -0.710/00 ±0.21‰(lσ), -4.950/00 ± 0.11‰(lσ) and 8.915± 0.046 mmol/mol (lσ). Variability in the fossil coral δ180 and Sr/Ca time series is diminished with respect to similar records in modem corals, which is consistent with previous predictions of fewer or less dramatic ENSO events in the early Holocene. Sea-surface temperature reconstructions based on coral δ180 and Sr/Ca indicate that surface water in the WPWP was cooler than modern by ~1.7°C at 8,000 years ago. Mass balance calculations indicate that seawater (dw) was 0.04‰less than modern day values, which translates to a ~ 0.5 p.s.u. decrease in sea surface salinity relative to modern.