ADVANCE Fellows Award: Investigating the Origins of Orbitally Forced Paleoclimates: The Interplay of Climate Response, Geodynamics, Astrodynamics and Earth Noise

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Hinnov 0137799 This ADVANCE Fellows career-development plan centers on an investigation of orbitally forced paleoclimate signals as carriers of first order geodynamical and astrodynamical information. Geodynamical theory predicts that the Earth's tidal dissipation and dynamical ellipticity will perturb the Earth's axial precession rate and tilt. The perturbations should appear in paleoclimatically recorded orbital modes as phasing irregularities. Observation of these irregularities depends upon the accuracy of the timescale assigned to the paleoclimate record. This typically involves adjusting an interpreted orbital signal in the record to a "target" curve based upon an assumed climate response to orbital forcing. If the target is wrong, however, timing errors will corrupt the true phasing of the recorded orbital modes. Until this source of error can be effectively managed, no firm conclusions about the Earth's physical behavior should be drawn from the paleoclimate record. Astrodynamical theory indicates that long-period amplitude and frequency modulations in the Earth's orbital modes track planetary orbital motions; these should be detectable in very long paleoclimate signals. Some planetary orbits resonate, e.g., Earth and Mars; in the remote past, the orbits of Mars and Earth may have moved chaotically between two resonance states. Verification of this behavior using the paleoclimate record is therefore a top priority in astrodynamics. Complicating the extraction of this information, however, is low frequency "Earth noise" that can interfere with long paleoclimate signals. To unravel these problems, a multi-task computer model will be developed that calculates insolation at any geographical location over any timescale, and is linked to adjustable rotational-orbital parameters that include effects from the Earth's tidal dissipation and dynamical ellipticity. The model will be explored in a series of sensitivity experiments, then evaluated against paleoclimate records using advanced time series analysis.