Cross-Wavelet Analysis: a Tool for Detection of Relationships between Paleoclimate Proxy Records

Cross-wavelet transform (XWT) is proposed as a data analysis technique for geological time-series. XWT permits the detection of cross-magnitude, phase differences (= lag time), nonstationarity, and coherency between signals from different paleoclimate records that may exhibit large stratigraphic unc...

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Bibliographic Details
Published in:Mathematical geosciences 2008-07, Vol.40 (5), p.575-586
Main Authors: Prokoph, Andreas, El Bilali, Hafida
Format: Article
Language:English
Subjects:
Carbon dioxide
Chemistry and Earth Sciences
Computer Science
Earth and Environmental Science
Earth Sciences
Fossils
Geological time
Geotechnical Engineering & Applied Earth Sciences
Hydrogeology
Noise levels
Paleoclimate
Paleontology
Physics
Special Issue
Spectral analysis
Statistics for Engineering
Stratigraphy
Time series
Wavelet transforms
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Summary:Cross-wavelet transform (XWT) is proposed as a data analysis technique for geological time-series. XWT permits the detection of cross-magnitude, phase differences (= lag time), nonstationarity, and coherency between signals from different paleoclimate records that may exhibit large stratigraphic uncertainties and noise levels. The approach presented herein utilizes a continuous XWT technique with Morlet wavelet as the mother function, allows for variable scaling factors for time and scale sampling, and the automatic extraction of the most significant periodic signals. XWT and cross-spectral analysis is applied on computer generated time-series as well as two independently sampled proxy records (CO 2 content approximated from plant cuticles and paleotemperature derived from δ 18 O from marine fossil carbonate) of the last 290 Ma. The influence of nonstationarities in the paleoclimate records that are introduced by stratigraphic uncertainties were a particular focus of this study. The XWT outputs of the computer-models indicate that a potential causal relationship can be distorted if different geological time-scale and/or large stratigraphic uncertainties have been used. XWT detect strong cross-amplitudes (∼200 ppm ‰) between the CO 2 and δ 18 O record in the 20–50 Myr waveband, however, fluctuating phase differences prevent a statistical conclusion on causal relationship at this waveband.
ISSN:1874-8961
1874-8953
DOI:10.1007/s11004-008-9170-8