Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 10, issue 7
Biogeosciences, 10, 5009-5017, 2013
https://doi.org/10.5194/bg-10-5009-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 10, 5009-5017, 2013
https://doi.org/10.5194/bg-10-5009-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Jul 2013

Research article | 24 Jul 2013

Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

M. Roland1, P. Serrano-Ortiz2,3, A. S. Kowalski3,4, Y. Goddéris5, E. P. Sánchez-Cañete2,3, P. Ciais6, F. Domingo2, S. Cuezva7, S. Sanchez-Moral8, B. Longdoz9, D. Yakir10, R. Van Grieken11, J. Schott5, C. Cardell12, and I. A. Janssens1 M. Roland et al.
  • 1Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
  • 2Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas (CSIC), Carretera de Sacramento s/n, 04120 Almería, Spain
  • 3Grupo de Física de la Atmósfera, Centro Andaluz de Medio Ambiente (CEAMA), Avenida del Mediterráneo s/n, 18006 Granada, Spain
  • 4Departamento de Física Aplicada, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada, Spain
  • 5Geosciences Environnement Toulouse (GET), Observatoire Midi-Pyrénées, CNRS, Avenue Edouard Belin 14, 31400 Toulouse, France
  • 6Laboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA CNRS UVSQ, Orme des Merisiers s/n, 91191 Gif-sur-Yvette, France
  • 7Departamento de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Campus de Sant Vicent del Raspeig, 03080 Alicante, Spain
  • 8Departamento de Geología, Museo Nacional Ciencias Naturales (MNCN-CSIC), José Gutiérrez Abascal 2, 28006 Madrid, Spain
  • 9Ecologie et Ecophysiologie Forestières (EEF), UMR1137, INRA, 54280 Champenoux et Université de Lorraine, 54500 Vandoeuvre Les Nancy, France
  • 10Environmental Sciences and Energy Research, Weizmann Institute of Science, 76100 Rehovot, Israel
  • 11Department of Chemistry, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
  • 12Departamento Mineralogía y Petrología, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada, Spain

Abstract. CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or nighttime CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil–atmosphere CO2 exchanges in dry regions \mbox{with carbonate soils}.

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