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www.clim-past-discuss.net/7/1363/2011/
doi:10.5194/cpd-7-1363-2011
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Systematic study of the fresh water fluxes impact on the carbon cycle
1Laboratoire des Sciences du Climat et de l'Environnement, IPSL-CEA-CNRS-UVSQ, UMR 8212, Centre d'Etudes de Saclay, Orme des Merisiers bat. 701, 91191 Gif Sur Yvette, France
2NCAS-Climate, Meteorology Department, University of Reading, Reading RG66BB, UK
3Faculty of Earth and Life Sciences, Section Climate Change and Landscape dynamics, Vrije Universiteit Amsterdam, De Boelelaan, 1085, 1081 HV Amsterdam, The Netherlands
Abstract. During glacial periods, atmospheric CO2 concentration rapidly increases and decreases by around 15 ppm at the same time as climate experiments an abrupt cooling in the North Hemisphere and warming in the South Hemisphere. Such a climate change can be triggered in models by adding fresh water fluxes (FWFs) in the North Atlantic. Yet the impact on the carbon cycle is less straightforward, and previous studies give opposite results. Because both models and added fresh water fluxes were different in these studies, it prevents any direct comparison and hinders finding an explanation for these discrepancies. In this study we use the CLIMBER-2 coupled climate carbon model to explore the impact of different additional fresh water fluxes in various conditions, including the experiments previously performed with other models. We show that the CO2 changes caused by the fresh water flux events should be interpreted as a combination of oceanic and terrestrial processes. The initial state of the Atlantic Meridional Overturning Circulation (AMOC) prior to the addition of fresh water fluxes appears to play a crucial role. The rapid increase of CO2 observed in ice core data can only be accounted for when the export of North Atlantic Deep Water (NADW) is relatively slow. Additionally, the terrestrial and oceanic carbon reservoirs responses are a consequence of the climate change and most importantly of the "seesaw" effect. As the latter is different in the various models it results in widely different evolution of the vegetation and oceanic carbon reservoirs. The discrepancies between the different studies can thus be explained by a combination of these factors: initial climatic and carbon cycle states, characteristics of the added fresh water flux, AMOC initial state and model "seesaw" pattern.
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Notice on Discussion StatusCitation: Bouttes, N., Roche, D. M., and Paillard, D.: Systematic study of the fresh water fluxes impact on the carbon cycle, Clim. Past Discuss., 7, 1363-1392, doi:10.5194/cpd-7-1363-2011, 2011. Bibtex EndNote Reference Manager XML
