Session: Cross-cutting Group 2 (Paleovar, Past to future, Data assimilation)
Author: Kenji Izumi / Kenji.Izumi@lsce.ipsl.fr / LSCE/IPSL
Co-author: Anne-Marie Lézine, LOCEAN/IPSL;
Basil Davis, Université de Lausanne;
Patrick Bartlein, University of Oregon;
The last deglaciation (from 21,000 to 9,000 years ago), during which the huge ice sheets over the North America and Scandinavia melted, is a period of tremendous climate and environmental changes. These changes are documented by physically based paleoenvironmental indicators (such as oxygen or carbon isotopes in ice cores and marine cores) and by biologically based data (such as paleo-vegetation). This study aims, for this period of the last deglaciation, at 1) building a comprehensive documentation of climate changes over terrestrial areas from widely available pollen data, 2) assessing the impact of both climate and atmospheric CO2 changes on vegetation change, and 3) investigating the changes in large-scale atmosphere circulation and the hydrological cycle responsible for these surface climate and vegetation changes. This study will provide new benchmarking data for understanding environmental changes and evaluating climate models that are used for climate projections. Then, these results will contribute to quantifying the range of possible changes in these circulations in the future.
Here, we develop pollen/biome-based global climate reconstructions with an inverse (equilibrium) vegetation modeling approach over the last deglaciation. The approach is implemented by searching for a set of climate values which, when input to a vegetation model, simulates vegetation that is consistent with the paleovegetation reconstructed from fossil pollen data. The approach allows us to avoid both no-analog and wrong-analog problems and to assess the potential bias in reconstructions that may result from varying atmospheric CO2 concentrations.