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Atmospheric chemistry; Carbon dioxide; Carbonates; Carbonation; Climate control; Earth (planet); Ecosystems; Lithology; Sedimentary rocks; Soils; Thermodynamics, Atmospheric concentration; Carbonate weathering; Chemical weathering; Climate; Climate condition; Global; Global carbon cycle; pCO2, Weathering
Abstract:
Carbonate rocks are a peculiarity of the Earth relative to other planets in the solar system. Large terrestrial areas are covered by carbonate lithology, which actively reacts with atmospheric/biospheric CO2. Although carbonate rocks represent a major component of the global carbon cycle, their intensity and rates of chemical weathering have been overlooked. In this study, we examine three global databases of rivers and springs draining carbonate regions under various climate conditions (from −15 °C to +30 °C). Using Ca2+ + Mg2+ concentrations as a proxy, we show that carbonate weathering intensity depends upon land temperature according to a boomerang-type relationship, with maximum dissolution between 10 and 15 °C. We show that this pattern is primarily controlled by thermodynamics if we assume that the partial pressure of CO2 in soil (pCO2) increases from atmospheric-like levels under cold climate up to 100 times the present day atmospheric concentration under hot climate. The link between soil pCO2 and land temperature is still not very well known, but by using three different published predictive soil pCO2 vs. T curves, we show that the boomerang shape can be, at least qualitatively, reproduced. This study shows that more data on carbonate weathering in various environments are needed to predict with more accuracy the role that carbonate lithologies and overlying ecosystems could play in the Anthropocene. © 2018 Elsevier B.V.
