Developing a coral proxy system model to compare coral and climate model estimates of changes in paleo-ENSO variability

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2019PA003836. This is version 4 of this Preprint.

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Authors

Allison Lawman , Judson Partin, Sylvia Dee, Christian Casadio, Pedro Di Nezio, Terrence Quinn

Abstract

Coral records of surface-ocean conditions extend our knowledge of interannual El Niño-Southern Oscillation (ENSO) variability into the pre-instrumental period. That said, the wide range of natural variability within the climate system as well as multiple sources of uncertainties inherent to the coral archive produce challenges for the paleoclimate community to detect forced changes in ENSO using coral geochemical records. We present a new coral proxy system model (PSM) of intermediate complexity, geared toward the evaluation of changes in interannual variance. Our coral PSM adds additional layers of complexity to previously published transfer functions of sensor models that describe how the archive responds to sea-surface temperature (SST) and salinity. We use SST and salinity output from the Community Earth System Model Last Millennium Ensemble 850 control to model coral oxygen isotopic ratios and SST derived from Sr/Ca. We present a detailed analysis of our PSM using climate model output for sites in the central and southwest Pacific before extending the analyses to span the broader tropical Pacific. We demonstrate how variable growth rates, analytical and calibration errors, and age model assumptions systematically impact estimates of interannual variance, and show that the relative magnitude of the change in interannual variance is location dependent. Importantly, however, we find that even with the added uncertainties in our PSM, corals from many circum-Pacific locations are broadly able to capture decadal and longer (decadal+) changes in ENSO variability. Our code is publicly available on GitHub to facilitate future comparisons between model output and coral proxy data.

DOI

https://doi.org/10.31223/osf.io/82vhj

Subjects

Climate, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Keywords

paleoclimate, climate proxies, corals, ENSO

Dates

Published: 2020-02-04 05:03

Last Updated: 2020-06-25 14:55

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License

Academic Free License (AFL) 3.0

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