[pccgrads] Alyssa Atwood on "Central Pacific Climate Change During the mid-Holocene: New insights from coral records and climate models" Fri 11/3 at 12:30 in OCN 425

UW PCC uwpcc at uw.edu
Wed Nov 1 08:30:37 PDT 2017

Special seminar on Friday, 3 November, given by School of Oceanography alum (PCC alum too!)

Alyssa R. Atwood
University of California, Berkeley

12:30 P.M., 425 Ocean Sciences Building

Central Pacific Climate Change During the mid-Holocene: New insights from coral records and climate models


The processes that control El Niño/Southern Oscillation (ENSO) variability on long timescales are still poorly understood. As a consequence, limited progress has been made in understanding how ENSO will change under increased greenhouse gas concentrations. The mid-Holocene provides a well-defined target to study the fundamental controls of ENSO variability. A large number of paleo-ENSO records spanning the tropical Pacific indicate that 3000-6000 yr BP, a time when Earth’s orbital parameters (namely, precession) were substantially different than today, ENSO variability was reduced by as much as 50% relative to modern times. However, while a weak mid-Holocene ENSO appears to be a robust feature in the paleoclimate record, evolution of the mean tropical Pacific climate is poorly constrained. While decades of research have demonstrated the fidelity of oxygen isotope records from tropical Pacific coral to quantify interannual temperature and precipitation anomalies associated with ENSO, substantial mean offsets exist across overlapping coral sequences that have made it difficult to quantify past changes in mean climate. Here, we test a new approach of reconstructing changes in mean climate from coral records using a large ensemble of bulk measurements on fossil corals from Kiritimati in the central equatorial Pacific that span the Holocene. In contrast to the traditional method of high-resolution sampling to reconstruct monthly climate conditions, we implement a bulk approach, which dramatically reduces the analysis time needed to estimate mean coral d18O and enables a large number of corals to be analyzed in the production of an ensemble of mean climate estimates. In addition to these bulk measurements, select high-res measurements were performed to constrain changes in the amplitude of the seasonal cycle. I will present preliminary results from this joint bulk/high-res sampling approach that provide new constraints on changes in mean climate and seasonality in the central equatorial Pacific over the last 6,000 yr BP. I will discuss these results in the context of recent idealized precessional forcing simulations that have been performed with fully coupled climate models.

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