Capturing Equatorial Pacific Variability With Multivariate Sr‐U Coral Thermometry
Name
Paleoceanog and Paleoclimatol - 2023 - Mollica - Capturing Equatorial Pacific Variability With Multivariate Sr‐U Coral.pdf
Description
Published version
Size
1.47 MB
Format
Adobe PDF
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Author(s)
Mollica, NR
Cohen, AL
Horton, F
Oppo, DW
Solow, AS
McGee, D
Date Issued
September 27, 2023
Journal
Paleoceanography and Paleoclimatology
Publisher
American Geophysical Union
Citation
Mollica, N. R., Cohen, A. L., Horton, F., Oppo, D. W., Solow, A. S., & McGee, D. (2023). Capturing equatorial Pacific variability with multivariate Sr-U coral thermometry. Paleoceanography and Paleoclimatology, 38, e2022PA004508.
Version
Final published version
Abstract
Sr-U, a coral-based paleothermometer, corrects for the effects of Rayleigh Fractionation on Sr/Ca by regressing multiple, paired U/Ca and Sr/Ca values. Prior applications of Sr-U captured mean annual sea surface temperatures (SSTs), inter-annual variability, and long-term trends. However, because many Sr/Ca-U/Ca pairs are needed for a single Sr-U value as originally formulated, the temporal resolution of the proxy is typically limited to 1 year. Here, we address this limitation by applying laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to three Porites colonies from Jarvis and Nikumaroro Islands in the central equatorial Pacific (CEP), generating ∼25 Sr/Ca-U/Ca pairs per month of skeletal growth. Both Sr/Ca and U/Ca vary significantly over small (sub-mm) length scales and support the calculation of Sr-U values using the original regression method. Over the represented temperature range of 24–31°C, the Sr/Ca-U/Ca-SST relationships are nonlinear, a finding consistent with predictions of the Rayleigh model. To reflect this non-linearity, we developed a calibration using multivariate nonlinear regression. The multivariate, three-coral calibration was applied to 20 years of monthly resolved Sr/Ca and U/Ca of a coral interval not included in the calibration, yielding RMSE = 0.73°C and r2 = 0.85 (p < 0.05; df = 256). The multivariate calibration performed significantly better than Sr/Ca alone (r2 = 0.28). Applying the new calibration to a subfossil Porites from Kiritimati Atoll, CEP (2200 Before Present) yields equivalent phase and amplitude of interannual variability, but water temperatures ∼1.6°C cooler than they are in this region today.
MIT Department
Woods Hole Oceanographic Institution
Joint Program in Applied Ocean Science and Engineering
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
10.1029/2022pa004508
