Paleoclimatic Reconstruction and Evaluation of Sub-Centennial Climate Variability in the Late Holocene Using Records from Massive Corals (New Caledonia), Tree-Rings (New Mexico) and Speleothems (China)
Degree Granting Department
Terrence M. Quinn, Ph.D.
Gary T. Mitchum, Ph.D.
Benjamin P. Flower, Ph.D.
David J. Hollander, Ph.D.
Richard Z. Poore, Ph.D.
Coral Sr/Ca, Tropical climate variability, Climate proxies, Time series analysis
This study focuses on how the construction of a paleoclimate time series influences the interpretation in the frequency domain. Three time series are examined: a New Caledonian coral (Amedee Island), a Chinese speleothem (Dongge Cave), and New Mexican trees (El Malpais).
This study presents a monthly resolved coral Sr/Ca time series from New Caledonia that reconstructs sea surface temperature (SST; 1648-1999). The chronology is based on density-band counting, cross-correlating Sr/Ca, and ²³°Th dating. The intracolony coral Sr/Ca variations are coherent on interannual to centennial time scales and are reproducible for >300 years. The SST reconstruction reveals estimated cooling trend (~0.4°C) from 1741-1815, a colder nineteenth century (~0.6°C), and a warming trend (~0.6°C) in the twentieth century. Spectral and wavelet analysis reveals significant inter-decadal periodicities (~14-21 years/cycle) that modulate with time, and nearly persistent multi-decadal periodicities (~25-33 years/cycle) that do not exhibit coherence with the Inter-decadal Pacific Oscillation. The multi-decadal periodicities may be a harmonic of the inter-decadal periodicities or may represent an independent mode not previously recognized.
The Dongge Cave time series is based on uneven time intervals between data points (∆t) requiring interpolation to a constant ∆t for analysis with traditional spectral methods. A comparison of the even and uneven ∆t spectra using the Lomb-Scargle transform reveals the interpolated spectrum contains suppressed periodicities (<20 years/cycle), in contrast to the uninterpolated spectrum, resulting in a steeper slope in the red noise model thus influencing significance testing.
The El Malpais time series is an average of tree-ring width series. Spectral analysis of the entire time series identified significant periodicities. However, significance varies between three temporal subsets, in which the number of series varies; therefore, these periodicities may be a function of the number of series or may represent a real temporal variability. Cross-spectral analysis of the El Malpais and Dongge Cave time series reveals significant coherence; however, cross-wavelet analysis, which examines localized frequencies in the time domain, reveals a lack of correlation; therefore, coherence in the frequency domain does not indicate correlation in the time domain.
Scholar Commons Citation
DeLong, Kristine Lee, "Paleoclimatic Reconstruction and Evaluation of Sub-Centennial Climate Variability in the Late Holocene Using Records from Massive Corals (New Caledonia), Tree-Rings (New Mexico) and Speleothems (China)" (2008). Graduate Theses and Dissertations.