Some Novelties in the Astronomical Theory over the Last Decades

Details Some Novelties in the Astronomical Theory over the Last Decades Some Novelties in the Astronomical Theory over the Last Decades

Dec 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufm.u11a..02b&link_type=abstract

American Geophysical Union, Fall Meeting 2001, abstract #U11A-02

Astronomy and Astrophysics

Astronomy

1620 Climate Dynamics (3309), 3344 Paleoclimatology, 4267 Paleoceanography

Scientific paper

The paper by Hays, Imbrie and Shackleton has triggered a lot of research over the last decades. These lead to new developments and to a generalisation of the Milankovitch theory. The Louvain-la-Neuve team has focussed mainly on the orbital parameters and the transient response of the climate system to the astronomically-induced insolation changes. The orbital solution available in the late 70's has been shown accurate for 1.5 million years and is extended now over a few million years. The prediction made in 1982 that " a time will come when geologists will provide astronomers with estimates of periodicities ... and discuss with them which paleoastronomical efects should be added to the gravitational model " is realized. The origin of all the fundamental frequencies characterizing the long-term variations of the orbital parameters has been identified allowing to discuss their interrelationship and possible changes in times. Different sources for the 100-kyr astronomical cycle can be found in the orbital parameters and in the insolation itself. Instability of the 100-kyr eccentricity cycle has been shown related to its 400-kyr cycle. The amplitude and frequency modulations of the orbital parameters are also discussed. The 2.5-D Climate model of LLN (one of the very first Earth models of intermediate complexity) has succeeded to simulate the entrance into glaciation 2.75 million years ago, the late Pliocene - early Pleistocene obliquity and precession cycles, the emergence of the 100-kyr cycle around 900 kyr BP, the glacial-interglacial cycles of the last 600 kyr, the stage 11-stage 1 analogy and the future climate at the astronomical time scale. Finally, the climate model points out that the length of the simulated MIS11 interglacial is very sensitive to the interplay between insolation and CO2, i.e. it depends strongly on the phasing between these two climate forcings. Although the present and near future insolation forcing is very similar to stage 11, the exceptionally long interglacial simulated for the future is much more robust. An higher resolution version of this model (including 3 oceanic basins and the thermohaline circulation) allows to discuss the climate of isotopic stage 5, the late glacial, the last deglaciation, the Holocene, the last 1000 years and the last and next 100 years.

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