HR: 0800h
AN: PP31A-0901    [Abstracts]
TI: Isotopic modelling of Heinrich Events : a method to constrain duration & freshwater release
AU: * ROCHE, D M
EM: roche@lsce.saclay.cea.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS Bat. 701 Orme des Merisiers, Gif s/s Yvette Cedex, 91191 France
AU: PAILLARD, D
EM: paillar@lsce.saclay.cea.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS Bat. 701 Orme des Merisiers, Gif s/s Yvette Cedex, 91191 France
AU: CORTIJO, E
EM: Elsa.Cortijo@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS Bat. 701 Orme des Merisiers, Gif s/s Yvette Cedex, 91191 France
AU: BROVKIN, V
EM: victor@pik-potsdam.de
AF: Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam, 14412 Germany
AB: During the last glacial period, abrupt climate events due to ice-sheet instabilities, called Heinrich events, are recorded in sediment cores retrieved in the north Atlantic. Model based studies have described likely physical mechanisms explaining these events, involving large-scale instabilities of the Laurentide (and fennoscandian) ice-sheets. But no general agreement exists on the characteristics of an Heinrich Event, in terms of duration and freshwater release. To further investigate this question, we have included oxygen-18 in a climate model of intermediate complexity, CLIMBER-2, to simulate Heinrich Event 4 (40kyr BP), enabling us a direct comparison with data. As the model used is a model of intermediate complexity, and therefore is fast to run, we compare a large ensemble of scenarii to oxygen-18 data measured in foraminiferal calcite of a comprehensive set of sediment cores to assess the duration, the rate of discharge and the contribution to sea-level rise of Heinrich Event 4. A statistical analysis is then used to minimize differences between model and data. Our approach enables us to diagnose these values with greatly reduced uncertainties. We show that Heinrich Event 4 lasted 250ñ150 years and released an amount of ice corresponding to about 2ñ1 meters sea level equivalent. Our results are in good agreement with the sum of arising sedimentological evidences that Heinrich events were shorter than a millennium. We demonstrated that during HE4 the only consistency between model results and data involves a complete, or nearly complete, shutdown of the THC. These results emphasizes the need for isotopic tracer simulation to analyze thoroughly paleo-records, allowing us to gain confidence in the model behavior during rapid climate changes. To pursue even further the comparison with data, we used the carbon cycle module of CLIMBER analyze the signal in terms of carbon 13. An interpretation of this comparison will be suggested. The implications of these result on the comprehension of the mechanisms of glacial climate variability will be investigated in the frame of succession of events.
DE: 4870 Stable isotopes
DE: 4267 Paleoceanography
DE: 4271 Physical and chemical properties of seawater
DE: 4532 General circulation
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting