Determining the driving forces behind climate change, as well as the sensitivity of Earth's climate system to these forces, is a central question in paleoclimate research. This study will provide the first explicit evaluation of changes in stochastic versus deterministic climate processes associated with the evolution of the Late Paleogene to Neogene climate system (36 Ma to the present). This timeframe was chosen because high quality, high resolution, continuous data are available for analysis, and because the interval spans the transition from a high pCO2 "Greenhouse" climate to a low pCO2 "Icehouse" world. The investigators focus on the analysis of published foraminiferal oxygen and carbon isotope records and use a number of techniques rooted in Thomson's multi-taper spectral method (MTM), as well as a suite of non-linear time series analysis methods. The project will generate several products: 1) a new high resolution benthic d18O composite record spanning 36 Ma to the present, 2) an analysis of the evolution of orbital signals over the same timeframe, and 3) a quantification of changes in stochastic climate variability during the Late Paleogene to Neogene, and an assessment of the relative dominance of deterministic orbital versus stochastic climate energy through the Greenhouse-Icehouse climate transition. Funding supports collaboration between a young PI and a senior female scientist, as well as graduate student training. The algorithms produced in the course of the research will be made publicly available as a resource for the broader climate science community.
Earth’s Climate Noise: A Key to Reconstructing Past Global Climate Change The astronomical forcing of climate change takes place over many thousands of years, and is due to deterministic periodic changes in sunlight distribution across Earth’s surface caused by changes in Earth’s orbit and rotation. Astronomical forcing was responsible for the growth and decay of the large polar ice sheets that took place over the past 36 million years. Much of the growth and decay occurred periodically from the deterministic astronomical forcing, but additionally, stochastic changes occurred in the ice sheets, related to the physics of climate change. These latter changes have been largely ignored in paleoclimate research. This study conducted a comprehensive analysis of stochastic climate variability over the past 36 million years by applying new computational approaches to evaluate paleoclimate data from the world’s oceans. The evolution of global climate during the past 36 million years is characterized first by a transition from warm conditions to the glaciation of Antarctica, and subsequently, to the much colder world of the past 1 million years, with large polar ice sheets in both Northern and Southern hemispheres. Results from this study provide new evidence for the history of growth and decay of these ice sheets, resolving previously ambiguous aspects of ice sheet development, and demonstrating linkages between stochastic processes and deterministic astronomical forcing. The project also evaluated evidence for linear and non-linear climate response to deterministic astronomical forcing, providing new climate "fingerprints" for climate models that can be used to test competing hypotheses for observed paleoclimate change.
