New Approaches to Reconstruct Past Oceanic Variations in the Eastern Equatorial Pacific

Abstract

The sea surface temperature (SST) of the Eastern Equatorial Pacific (EEP) can influence the global climate system through different modes of climate variability. Paleoclimate records allow us to study how these regions have changed over long timescales. Yet, there is a lack of paleoclimate record in the EEP, and the fidelity of the proxies commonly used have been questioned. In this study, we use an inductively coupled plasma – optical emission spectrometer (ICP-OES) to generate elemental records (Sr/Ca, Li/Mg, Ba/Ca) from two corals collected in the Galapagos Archipelago and analyze their fidelity to reconstruct past oceanic variations. We show that ICP-OES can measure all targeted elements, but with substantial uncertainty. Sr/Ca remains a robust SST proxy and is more precise and accurate than Li/Mg. Nevertheless, combining Sr/Ca and Li/Mg can help us better reconstruct SST. Although previous work has suggested a link between upwelling and Ba/Ca, we find no such relationship. Our results suggest that reducing analytical uncertainties in ICP-OES can potentially open the door to a rapid approach to carry out multiproxy reconstruction in corals. Our results also caution the use of Ba/Ca as an upwelling indicator.