Natural and Anthropogenic Driving Forces of Carbonate Weathering and the Related Carbon Sink Flux: A Model Comparison Study at Global Scale
Sibo Zeng, Georg Kaufmann, Zaihua Liu
Abstract
Abstract The continental weathering process is driven by environmental factors such as changes in temperature, moisture, and CO 2 concentration, which can have natural (climate) or anthropogenic (land‐use) origins. In this paper, we attempt to evaluate the global applicability of different environmental drivers, which can be used to estimate the global carbonate dissolution intensity (bicarbonate concentration, (HCO 3 − ), as a proxy) and the related carbon sink flux (CCSF). We employ three ecological models and a series of satellite‐based databases, which provide estimates on soil CO 2 ‐concentrations ( p CO 2 ). By using the three parameterized p CO 2 , global temperature (T) and runoff (N), we obtain similar global averages for (HCO 3 − ) and CCSF, ranging from 2.73 to 2.81 mmol L −1 and 4.52–5.36 t C km −2 yr −1 . We compare our calculated (HCO 3 − ) to observed carbonate spring records. The results indicate that the net primary production based p CO 2 (NPP‐ p CO 2 ) model is more accurate for simulating (HCO 3 − ) in most boreal and temperate ecosystems, while the soil‐water content based p CO 2 (SWC‐ p CO 2 ) model may perform better in forests. According to the findings in this study, we stress that natural and anthropogenic factors are strongly intertwined in shaping global (HCO 3 − ) and CCSF patterns. Due to the crucial role of human land‐uses in p CO 2 and water yield, future human land‐use changes may be as significant as natural climatic changes for carbonate weathering and thus the relevant carbon sink.