HR: 1340h
AN: B23B-1271    [Abstracts]
TI: Estimating the impact of natural and anthropogenic changes on the transfer of elements from the continent to the ocean at the large watershed scale in a tropical environment
AU: Godderis, Y
EM: godderis@astro.ulg.ac.be
AF: LMTG CNRS-University of Toulouse, Observatoire Midi-Pyrénées 14 avenue Edouard Belin, Toulouse, 31400, France
AU: * Roelandt, C
EM: roelandt@lmtg.obs-mip.fr
AF: LMTG CNRS-University of Toulouse, Observatoire Midi-Pyrénées 14 avenue Edouard Belin, Toulouse, 31400, France
AU: Bonnet, M
EM: bonnet@lmtg.obs-mip.fr
AF: LMTG CNRS-University of Toulouse, Observatoire Midi-Pyrénées 14 avenue Edouard Belin, Toulouse, 31400, France
AB: Continental weathering of silicate rocks has been recognized as a major driver of climatic changes at the geological timescale. New evidences and preliminary modelling works [1] show that the impact of continental weathering on the geochemical cycles and climate might be non negligible at shorter time scales, from 10² to 10⁴ years, with for instance an increase in total continental weathering by 12 percent from the LGM towards the present day [2]. Continental weathering at large scale (10⁶ km²) is generally described through parametric laws (see for instance [3]), linking weathering rates to mean annual air temperature and continental runoff. These laws are masking numerous other parameters, implicitly included, such as the role of vegetation and physical erosion, and limits the ability of those models to predict changes in weathering due to anthropogenic impacts. A coupled model of biospheric and weathering processes has been developped to estimate the transfer of elements to the ocean originating from tropical watersheds. The BERNI model is the result of the coupling of LPJ - dynamic global vegetation model [5] with the WITCH model [6] that estimates dissolution/precipitation of minerals in the soil environment from kinetic laboratory laws. Here we present results obtained for the Orinoco watershed. Output of the coupled model includes major ion concentrations that are compared to available data, and CO2 consumption through weathering for a tropical environment. The impact of land use changes is tested, as well as the response of weathering to climatic change at continental scale. [1] Aumont et al. (2001) GBC15, 393-405. [2] Burton K.W. et al. (2006) EGU General Assem., Vienna [3] Dessert C. et al. (2003) Chem. Geol.202, 257-273. [4] Edmond et al. (1995) GCA59, 3301-3325; Millot et al. (2002), EPSL196, 83-98. [5] Sitch S. et al. (2003) Global Change Biology 9, 161-185. [6] Goddéris et al. (2006) GCA70, 1228-1147.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1030 Geochemical cycles (0330)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting