Three-dimensional visualization of orbital forcing and climatic repsonse: Interactively exploring the pacemaker of the ice ages

Abstract

Recent developments in continuous core-logging techniques now permit us to recover the high-resolution time series necessary for the detailed spectral analyses of paleoclimatic proxy records. When applied to long records recovered by scientific drilling (5–10 Ma) they enable us to look at the long-term history and evolution of the ocean’s response to orbital forcing. A serious limitation in these studies is the need to display the complex, multidimensional spatial and temporal interactions of the ocean-climate system in an easily comprehensible manner. We have addressed this issue by developing a series 3D visualization tools which permit visualization of the role of the orbital parameters in determining the latitudinal variation of insolation as well as the interactive exploration of multidimensional data sets. The ORBITS tool allows us to visualize the effect of orbital eccentricity, precession, and tilt on the latitudinal distribution of insolation on the earth at the solstices and the equinoxes for any time over the past 5 Ma (for Berger’s orbital model) or 10 Ma (for Laskar’s orbital model). The effect of the orbital parameters on insolation can be viewed individually, in pairs, or all three together. By moving the model steadily through time, the rate at which orbitally induced changes in insolation occur can also be visualized. To look at the ocean’s response to orbital forcing we take the long time series generated from our paleoclimatic proxies and calculate their spectrum over a fixed, but sliding, time window. To view the complex multidimensional relationships found in these evolutionary spectral analyses, we use another interactive 3D data exploration tool developed at the University of New Brunswick (Canada). This tool (FLEDERMAUS) uses a six-degrees-of-freedom input device (BAT) and a series of software modules for color coding, shading, and rendering complex data sets, to allow the user to interactively “fly” through the multidimensional data. Through the use of color, texture, and 3D position, as many as six or seven variables can be explored in a simple and intuitive manner. With special liquid-crystal-display glasses, the scene can be viewed in true “stereo.” We use these tools to explore the relationship between orbital forcing and the response of the benthic isotope and calcium carbonate record at ODP Site 846 (90°W and 5°S) This analysis shows an equatorial Pacific carbonate record which has a large component of linear response to tilt, but little linear response to precession. There is a major shift in response, from a carbonate-dominated response to an isotope (ice volume)-dominated response at approximately 4.5 Ma, and as expected, there is a large nonlinear response at the lower frequencies (400 and 100 kyr) during the past 800 kyr to 1 Ma