A wavelet investigation of possible orbital influences on past geomagnetic field intensity

A number of sedimentary records of relative geomagnetic palaeointensity have been reported to contain modes of variability that could have been driven by changes in the Earth's orbital or climatic state. When discussing hypothesized connections it is not common for the phase relationship between palaeointensity and orbital change to be addressed, so a true mechanistic link cannot be confirmed. Cross-wavelet analysis showed us that although the strength of the geomagnetic vector contains modes of variability with periods similar to orbital parameters there is no obvious direct causal relationship between them.

Cross-wavelet transform (left column) and squared wavelet coherence (right column) to compare the climate and paleointensity series in the time-frequency plane. The four time series employed in the study are, ETP (record of the Earth's orbital geometry), SPECMAP (planktonic oxygen-isotope stack), Sint-800 (a global stack of sedimentary relative palaeointensity records) and Seafloor (palaeointensity based on an inverted stack of seafloor magnetization)

The palaeointensity data from available archives spanning the past ~800 kyr suggest that changes in orbital parameters / global climatic conditions did not influence the geodynamo sufficiently to exert a detectable linear influence on the magnitude of the recorded field vector. This work will be developed further with the aim of detecting non-linear links between orbital configuration and the state of the geodynamo.