Journal Article

Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

Sanchez-Moral, S, Departamento de Ciencias de la Tierra y del Medio Ambiente [Universidad de Alicante] ; Universidad de Alicante, Departamento de Fisica Aplicada [Granada] ; Universidad de Granada = University of Granada (UGR), Museo Nacional de Ciencias Naturales [Madrid] (MNCN) ; Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain] (CSIC), Ecologie et Ecophysiologie Forestières [devient SILVA en 2018] (EEF) ; Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Institute for Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen); Spanish Ministry of Science and Innovation; Spanish Ministry of Science and Innovation, research programme Juan de la Cierva, Domingo, F, Weizmann Institute of Science [Rehovot, Israël], Ciais, Philippe, Longdoz, Bernard, Universiteit Antwerpen = University of Antwerpen [Antwerpen], Sanchez-Canete, E. P, Roland, M, van Grieken, R, Cardell, C, Laboratoire des Sciences du Climat et de

2013

Overview

CO$_2$ 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, CO$_2$ exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or night-time CO$_2$ uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO$_2$ exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO$_2$ 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 CO$_2$ outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO$_2$ exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO$_2$2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO$_2$ production. At night, ventilation ceases and the depleted CO$_2$ concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO$_2$ 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 CO$_2$ exchanges in dry regions with carbonate soils.

• Publisher: European Geosciences Union,CCSD,Copernicus GmbH,Copernicus Publications
• Subject: Analysis / Atmosphere / Atmospheric turbulence / Carbon dioxide / Carbonates / Climate change / Earth sciences & physical geography / Geochemistry / Karst / Life Sciences / Money / Physical, chemical, mathematical & earth Sciences / Physique, chimie, mathématiques & sciences de la terre / Sciences de la terre & géographie physique / Soils / Terrestrial ecosystems / Turbulence (Fluid dynamics) / Ventilation / Weathering
• ISBN: 0003222427000