RAPID: Sampling corals threatened by extreme El Nino warming for climate reconstruction (Galapagos, Ecuador)

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This project supports the collection of coral samples from the Galapagos National Park, in Ecuador. The Galapagos are experiencing a period of exceptionally strong warm ocean temperatures, related to the phenomenon known as El Niño that recurs every few years. In the past, such warm conditions have resulted in widespread death of corals, followed by the erosion of those skeletons by other marine animals. The skeletons of the corals themselves are valuable for climate research: the chemistry of the skeleton reflects the conditions under which the coral grew, and the corals have persisted for several decades. This project will sample and analyze these coral skeletons for climate history before erosion can damage them. The samples from modern corals will be compared with fossil coral records from the same region to better understand how the El Niño phenomenon is responding to the warming of the global climate. Broader impacts include field experience for a graduate student, support for undergraduate research, and collaborations with a local student and Park ranger at the Galápagos National Park and Charles Darwin Research Station. This RAPID project supports coral sampling in the central Galápagos archipelago, where an ongoing strong El Niño event threatens the preservation of coral-based climate records that are critical to quantify past and ongoing changes in El Niño/Southern Oscillation (ENSO) variability. Coral cores preserve quantitatively useful information about past climate variability in the geochemistry of their aragonite (CaCO3) skeletons. The Galápagos lie in the heart of the eastern equatorial Pacific where ENSO extremes create the largest sea surface temperature anomalies. The strong ENSO events of the late 20th century triggered massive coral mortality across the archipelago, e.g. >95% in 1982-3. The corals that have regrown over the past ~40 years contain valuable records of local sea surface temperature variability that are critically important to place paleoclimate records in context. These corals are likely to be stressed and degraded beyond the point of usefulness under the exceptionally warm conditions in Galápagos that has characterized the past several months (and is still ongoing). Previous work on Galapagos corals, both fossil and modern, documents unprecedented increases in ENSO intensity in the last 40 years, relative to the past millennium. Although the recent history of sea surface temperature from instrumental and satellite measures is known, modern coral records are needed to quantify the change over time and relate directly to fossil records. This project will also explore whether central Galapagos corals preserve a signal of ocean circulation – the isotopically distinct Equatorial Undercurrent. If detectable in coral data, this signal would add an important dynamical component to the interpretation of past change in ENSO variability. Coral paleoclimate results from the central archipelago that postdate the 1982 El Niño have never been published. The project trains a mid-career graduate student in field methods and will bring samples into a lab where undergraduates will gain experience in sampling and analyzing them. Project results in the Galápagos will be disseminated through broad channels, including public talks and Spanish-language presentations at the Galápagos National Park. 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.