Constraining astronomical models with geological data
Lead Research Organisation:
University of Southampton
Department Name: Sch of Ocean and Earth Science
Abstract
Just as tree rings can be used to count astronomical years back into the past, and ancient coral growth rings can be used to estimate the number of days per year in the past, layers of undisturbed sedimentary rocks can potentially record cyclical variations in the orbital configuration of Earth and other planets. These astronomical variations affect the amount of sunshine received at the top of the atmosphere, filtered through the climate system (e.g. ice ages), which finally influences the amount and type of sediment deposited in, e.g., the deep sea. Changes of these astronomical parameters: the Earth's eccentricity, obliquity (tilt), and climatic precession (wobble of the spin axis similar to a spinning top), occur on time scales of thousands to hundreds of thousands of years. The necessary geological records from the deep sea have only recently become available through the international Ocean Drilling Program, which recovers sediment cores from hundreds of metres below the sea bed in waters several kilometers deep. However, although we expect seasons to change very regularly every year, the solar system configuration of predominantly the inner planets is less regular on time scales of millions of years - it has been shown that it is 'chaotic'. This means that it is not possible to calculate aspects such as the changing tilt of the Earth's axis back in time indefinitely. This hinders geologist's efforts to use these changes as 'metronome' or pace-maker to estimate time. The aim of this research is to use characteristic patterns in the sedimentary record to extract astronomical parameters that can be used to extend the time scale over which model calculations are valid. This is important in order to constrain basic physical parameters that cannot be obtained otherwise by astronomers. More specifically, we hope to find several distinct occurrences of chaotic behaviour from deep sea sediment data during the past 30-50 million years that, in the extreme case, would even allow astronomers to very accurately test the predictions of Einstein's general relativity. The research proposed here would be accomplished through a novel collaboration between astronomers and Earth scientists. One additional aim of our proposed research is to constrain the evolution of the astronomical Earth model: due to the dissipative tides in the oceans, the solid parts of the Earth, Moon and Sun, as well as redistribution of mass on Earth due to, e.g. ice-ages and mantle convection, the rotation of the Earth is changing, and generally slowing down with time. Due to conservation of energy, this process also results in an increasing distance between the Earth and Moon, currently a few centimetres per year. In order to accurately calculate the orbital configuration and variations of the solar system, and the Earth in particular, it is important to constrain how strong this change in the Earth's rotation has been in the past. Again, just as tree rings can give information about dry and humid years, the detailed pattern of climate indicators recorded in sediments can be used to extract parameters of the Earth model in the past. We can now use newly available sediment cores, and additional measurements, to obtain important information for astronomers.
Organisations
People |
ORCID iD |
Heiko Pälike (Principal Investigator) |
Publications
Backman J
(2008)
Age model and core-seismic integration for the Cenozoic Arctic Coring Expedition sediments from the Lomonosov Ridge
in Paleoceanography
Bickle M
(2010)
Secrets of the sea floor
in Nature Geoscience
Boulila S
(2012)
A ~ 9 myr cycle in Cenozoic d13C record and long-term orbital eccentricity modulation: Is there a link?
in Earth and Planetary Science Letters
Charles A
(2011)
Constraints on the numerical age of the Paleocene-Eocene boundary AGE OF THE P-E BOUNDARY
in Geochemistry, Geophysics, Geosystems
Deconto RM
(2008)
Thresholds for Cenozoic bipolar glaciation.
in Nature
Liebrand D
(2011)
Antarctic ice sheet and oceanographic response to eccentricity forcing during the early Miocene
in Climate of the Past
O'Regan M
(2008)
Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge
in Paleoceanography
Pälike H
(2012)
A Cenozoic record of the equatorial Pacific carbonate compensation depth.
in Nature
Pälike H
(2008)
Orbital scale variations and timescales from the Arctic Ocean
in Paleoceanography
Pälike H
(2008)
Rock clock synchronization
in Nature Geoscience
Sangiorgi F
(2008)
Cyclicity in the middle Eocene central Arctic Ocean sediment record: Orbital forcing and environmental response
in Paleoceanography
Sexton PF
(2011)
Eocene global warming events driven by ventilation of oceanic dissolved organic carbon.
in Nature
Spofforth D
(2008)
Paleogene record of elemental concentrations in sediments from the Arctic Ocean obtained by XRF analyses
in Paleoceanography
Spofforth D
(2010)
Organic carbon burial following the middle Eocene climatic optimum in the central western Tethys ORGANIC CARBON BURIAL FOLLOWING MECO
in Paleoceanography
Toffanin F
(2011)
Changes in calcareous nannofossil assemblages during the Middle Eocene Climatic Optimum: Clues from the central-western Tethys (Alano section, NE Italy)
in Marine Micropaleontology
Wade B
(2011)
Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale
in Earth-Science Reviews