Reconstruction of NAO Variability in the Western Atlantic

Konrad Hughen, Marine Chemistry & Geochemistry

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Abstract

Climate systems including the North Atlantic Oscillation (NAO), among others, are known to affect sea surface temperature (SST) and sea surface salinity (SSS) in the northern Caribbean region with distinct seasonal signatures. The NAO exerts a particularly strong influence on Caribbean winds, SST and precipitation, mostly concentrated within the winter season. Understanding decadal-to-centennial scale variability in these climate systems is critical to predicting their future behavior, yet instrumental climate records are too short to capture this variability. Paleoclimate records with full seasonal resolution are thus critical for identifying signatures of regional forcing in winter and summer averaged climate data. Coral skeletons provide accurate chronologies from annual banding, high temporal resolution from rapid linear extension rates, and full capture of the entire seasonal cycle in geochemical records. Coral strontium–calcium ratios (Sr/Ca) have been shown to reliably record SST, and long paleotemperature records have been constructed recently, demonstrating the utility of Atlantic corals in reconstructing past oceanography.
 
This proposed research will create new monthly-resolution records of SST and NAO variability from Siderastrea siderea coral cores recovered from the southern coast of Cuba. Preliminary work demonstrates the fidelity of Sr/Ca in capturing monthly and interannual (winter season) variability in SST at this location. Furthermore, instrumental winter SST for this site is shown to reflect long-term variability in the NAO, suggesting that coral records will reflect NAO variability over the past 220 years. A better understanding of long–term variability in regional climate systems is critical to attributing and quantifying the contribution of anthropogenic forcing to recent global climate change and predicting changes in the future. A version of this proposal to NSF P2C2 was declined recently, possibly because the research effort was “too small”, although reviews are not yet released. If successful, this proposed work would establish the viability of coral paleoclimate records in the waters surrounding Cuba and the Gulf of Mexico region overall, paving the way for proposals to NSF and other external (private) entities for future research on regional climate variability.