EPHE Department Paleoclimatology  and Marine Paleoenvironments
Long-term climate changes

    Glacials and interglacials over the last 1,3 million years

     Documenting the variability of the different interglacials and glacials, specifically, their duration and amplitude allow us to assess the variety of responses that slightly different external forcing and feedback mechanisms produce on the different Earth’s reservois and, in particular, on vegetation dynamics and marine ecosystems.
 
    This topic includes the study of deglaciations and glacial inceptions under different climate boundary conditions (insolation, greenhouse gaz concentration and ice-sheet configuration) from Marine Isotopic Stage 38 to our present interglacial.
Comparison between Vigo (MIS 11) and Iberian Eemian (MIS 5) interglacials from the twin cores MD01-2447 and MD99-2331 (Desprat et al., 2005). MIS 5 data are from Sanchez Goni et al. 2005 and Gouzy et al., 2004, and insolation data from Berger, 1978.
The end of the warmest period of MIS 5 and 11 (orange bands) sees the glacial inception which coincides with the replacement of warm deciduous forest by a mixed deciduous (oak-hornbeam)-conifer (pine-fir) forest developed in northwestern Iberia. This vegetation change corresponds to the southward migration of the tree line in high latitudes in response to declining summer insolation which occurred before the substantial ice accumulation as shown by benthic d18O. Model-data comparison have shown that this vegetation change is a major feedback mechanism for glaciation initiation during MIS 5 as well as during MIS 11 when insolation changes are weak and cannot account alone for ice growth (Sanchez Goni et al. 2005; Desprat et al., 2005).