A long-term numerical solution for the insolation quantities of the Earth

Abstract

Abstract. We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from −250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al. 1993) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth-Moon System. The orbital solution has been used for the calibration of the Neogene period (Lourens et al. 2004), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth's motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about 0.38 degree in the next few millions of years, due to the crossing of the s 6 + g 5 − g 6 resonance (Laskar et al. 1993). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to g 2 − g 5 , with a fixed frequency of 3.200 /yr, corresponding to a period of 405 000 yr. The uncertainty of this time scale over 100 Myr should be about 0.1%, and 0.2% over the full Mesozoic era.

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…and 138e155 kyr ago intervals for the LGM and PGM, respectively. LGM and PGM minima for summer insolation and energy at 65 N were determined directly from the original datasets (Laskar et al, 2004;Huybers, 2006) through the same time intervals. In our analysis we also considered deep-sea benthic foraminiferal carbonate d 18 O from a stack of 57 globally distributed global records (Lisiecki and Raymo, 2005): PGM and LGM maxima are reported as anomalies (Dd 18 O benthic ) with respect to the mean of the most recent 2 kyrs.…”

“…Ice-sheet nucleation may, in addition, depend on chaotic aspects of the weather/climate system; for example, successive winters with heavy snowfall may e almost randomly e cause some locations to receive an initial snow cover with enough volume and albedo feedback to ensure its survival and subsequent growth potential (e.g., Oglesby, 1990). Finally, modelling studies (e.g., Abe-Ouchi et al, 2013) indicate that glacial culminations like the PGM and LGM reflect the outcome of temporal developments in forcings and feedbacks through the preceding glacial cycle that include insolation (e.g., Laskar et al, 2004;Colleoni et al, 2011), CO 2 and CH 4 concentrations (Monnin et al, 2001;Loulergue et al, 2008; Waelbroeck et al, 2002;Rohling et al, 2009Rohling et al, , 2014Elderfield et al, 2012;Grant et al, 2014), and also in state variables such as surface and deep-sea temperature (e.g., Stenni et al, 2010;Elderfield et al, 2012;Parrenin et al, 2013;Rohling et al, 2012Rohling et al, , 2014Martínez-Botí et al, 2015;Snyder, 2016a,b). Climate simulations by Colleoni et al (2014) suggest that orbital and greenhouse-gas changes for the penultimate glacial cycle were more favourable for glacial inception over Eurasia than over North America, relative to the last glacial cycle.…”

Forcing of wet phases in southeast Africa over the past 17,000 years

“…2g) over southern Africa 25 . Higher insolation intensifies atmospheric convection leading to higher rainfall over southern Africa 26 .…”

Late Oligocene obliquity-paced contourite sedimentation in the Wilkes Land margin of East Antarctica: implications for paleoceanographic and ice sheet configurations

“…This method allows the detection of non-stationary spectra variability within the time series. The time series were 255 analysed in the depth scale and then anchored to the obliquity solution (Laskar 2004) to transform them to an age scale, with the basis of the already resolved age model. The Evolutionary Average Spectral Misfit method was then used to resolve unevenly sampled series and changing sedimentation rates (Meyers et al, 2012).…”

“…This method is used to test a range of plausible timescales and simultaneously evaluate the reliability of the presence of astronomical cycles. The eccentricity, obliquity and precession 260 target periods were determined from La04 (Laskar et al, 2004) using the interval from 25.0 -26.4 Ma (Supplemental material S2).…”