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Little Ice Age Climate in the Western Tropical Atlantic Inferred from Coral Geochemical Proxies

Alice Alpert, Ph.D., 2016
Delia Oppo, Co-advisor
Anne Cohen, Co-advisor

Paleoclimate archives allow improved understanding of the rate, nature and extent by which anthropogenic warming will impact natural and human systems. Coral skeletons are high-resolution archives of tropical sea surface temperatures (SSTs), but inconsistencies call the accuracy of existing coral proxy records into question.

I quantify the errors associated with the traditional coral thermometer, Sr/Ca, and show that intercolony disparities are due to “vital effects” that result in a ± 2 ̊C uncertainty on reconstructed SST.

I then expand, refine, and test a new paleothermometer, Sr-U, across multiple coral species and through time. I show that Sr-U captures spatial SST variability with an uncertainty of ± 0.6 ̊C. and captures the mean SST and the 20th century trend in the Western Tropical Atlantic (WTA).
I apply Sr-U to a coral from the Little Ice Age (LIA) to address uncertainties in the magnitude of WTA cooling. Results suggest that 1465-1560 mean SST in the region was 1.1 ̊C±0.6°C cooler than the 1958-1988 mean, but within error of early 20th century SST at this site. My record demonstrates the value of Sr-U and the need for continuous accurate SST records to better constrain the amplitude, drivers, and mechanisms of LIA climate change.