Temperature and variability of the Atlantic Warm Pool during and since the Little Ice Age

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Surface ocean heat in the western tropical Atlantic, specifically the Atlantic Warm Pool (AWP) region, fuels Atlantic hurricane activity and exerts strong influence on rainfall in the northeastern Pacific, Central America, and southeastern United States. How the size and temperature of the AWP responds to climate change, however, is not well-understood, in large part because the instrumental record of ocean temperature is too short to enable accurate evaluation of variability on the decadal and multi-decadal timescales over which climate change occurs. Massive long-lived corals that grew on reefs in the AWP record this information in the geochemistry of their skeletons. This project will utilize a newly developed coral paleothermometer, Sr-U, to reconstruct continuous records of temperature in the AWP during and since the Little Ice Age (the last ~500 years). The project includes mentorship of a postdoctoral researcher and two graduate students from the Autonomous University of Mexico (UNAM) and University of Puerto Rico (UPR) who will participate in fieldwork, laboratory analyses and manuscript preparation. A successful outcome will provide the data needed to characterize the influence of anthropogenic warming on the AWP and to evaluate the skill of model projections of future climate change in the Atlantic sector. As the second largest body of warm water on the planet, the AWP exerts a significant influence on climate. Sea surface temperatures (SST) in the western tropical AWP are correlated to the Atlantic Multidecadal Oscillation (AMO), hurricane intensities and precipitation anomalies in the northeastern Pacific, Central America, and southeastern United States. Yet, the pre-20th century SST evolution of the AWP is poorly constrained, limiting our understanding of the sensitivity of AWP temperature, size, and variability to the natural and anthropogenic forcing of climate. This project will apply a novel new coral paleothermometer, Sr-U, to reconstruct continuous records of SST over the past 500 years using corals sampled at three locations ideally placed to study the expansion and contraction of the AWP on multidecadal time scales. The new data, from corals collected near the eastern Yucatan Peninsula, US Virgin Islands and Bahamas, will enable evaluation of the timing and nature of the anthropogenic imprint on the AWP, the persistence of multi-decadal variability in the AWP, the sensitivity of AWP SSTs to solar, volcanic and internal forcing, and the link between AWP and Atlantic hurricane variability. SST records from these three sites will also provide new evidence for the overall magnitude of LIA cooling in the WTA, a subject of great uncertainty, and be used to evaluate the skill of model projections of future climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.