HR: 0800h
AN: C51A-0109    [Abstracts]
TI: Ice Cores Dating With a New Inverse Method Taking Account of the Flow Modeling Errors
AU: * Lemieux-Dudon, B
EM: lemieux@lgge.obs.ujf-grenoble.fr
AF: Laboratoire de Glaciologie et de Geophysique de l'Environnement, CNRS, 54 rue Moliere, St Martin d'Heres, 38402, France
AU: Parrenin, F
EM: parrenin@lgge.obs.ujf-grenoble.fr
AF: Laboratoire de Glaciologie et de Geophysique de l'Environnement, CNRS, 54 rue Moliere, St Martin d'Heres, 38402, France
AU: Blayo, E
EM: Eric.Blayo@imag.fr
AF: Laboratoire Jean Kuntzmann, 51 rue des Mathematiques, Grenoble, 38041, France
AB: Deep ice cores extracted from Antarctica or Greenland recorded a wide range of past climatic events. In order to contribute to the Quaternary climate system understanding, the calculation of an accurate depth-age relationship is a crucial point. Up to now ice chronologies for deep ice cores estimated with inverse approaches are based on quite simplified ice-flow models that fail to reproduce flow irregularities and consequently to respect all available set of age markers. We describe in this paper, a new inverse method that takes into account the model uncertainty in order to circumvent the restrictions linked to the use of simplified flow models. This method uses first guesses on two flow physical entities, the ice thinning function and the accumulation rate and then identifies correction functions on both flow entities. We highlight two major benefits brought by this new method: first of all the ability to respect large set of observations and as a consequence, the feasibility to estimate a synchronized common ice chronology for several cores at the same time. This inverse approach relies on a bayesian framework. To respect the positive constraint on the searched correction functions, we assume lognormal probability distribution on one hand for the background errors, but also for one particular set of the observation errors. We test this new inversion method on three cores simultaneously (the two EPICA cores : DC and DML and the Vostok core) and we assimilate more than 150 observations (e.g.: age markers, stratigraphic links,...). We analyze the sensitivity of the solution with respect to the background information, especially the prior error covariance matrix. The confidence intervals based on the posterior covariance matrix calculation, are estimated on the correction functions and for the first time on the overall output chronologies.
DE: 0545 Modeling (4255)
DE: 0560 Numerical solutions (4255)
DE: 0724 Ice cores (4932)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2007 Fall Meeting