Temperature and CO2 dependency of global carbonate weathering fluxes – Implications for future carbonate weathering research.

Romero-Mujalli, G. , Hartmann, J. and Börker, J. (2019) Temperature and CO2 dependency of global carbonate weathering fluxes – Implications for future carbonate weathering research. Open Access Chemical Geology, 527 . Art.Nr. 118874. DOI 10.1016/j.chemgeo.2018.08.010.

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Carbonate weathering and transfer of carbon towards the coastal zone is one of the relevant sinks for atmospheric CO2, controlled by hydrology, ecosystem respiration, river water degassing, and further factors. Specifically, the connection between the soil-rock system to the river systems and instream processes affecting the weathering product fluxes remain under-researched. Based on constraints for soil-rock PCO2, river PCO2, and an identified dependence of river alkalinity on temperature, this work tested which controls should be considered at the global scale to accomplish a more holistic carbonate rock weathering model. Compiled river data suggests that with increasing land temperature, above approximately 11 °C, the amount of instream alkalinity in carbonate catchments decreases due to the temperature effect on the carbonate system, while the converse holds true at lower temperatures. Latter is in accordance with calcite dissolution controlled by soil-rock PCO2 estimates based on ecosystem respiration. In addition, the type of the weathering system (open, semi-closed to closed system with respect to CO2) was identified to be highly relevant for global weathering estimations. Open systems seem to be the most dominant boundary condition of calcite weathering in the soil profile. Tropical areas with thick soil layers, however, cause the carbonate weathering system to shift from open to semi-closed or closed system conditions. The findings support that calcite weathering fluxes in the soil profile are higher than the fluxes to the ocean transported by rivers. Furthermore, an increase in mean land temperature does not necessarily translate into an increase of lateral weathering fluxes because it might have an influence on soil development, discharge, CO2 degassing, soil respiration and calcite dissolution. All these named factors need to be addressed to be able to quantify global carbonate weathering fluxes and to assess the sensitivity of carbonate weathering fluxes on climate variability. Future works should focus on collecting more temporal river chemistry data, mainly in tropical regions, to understand the main mechanism causing the observed decrease of alkalinity concentration with temperature.

Document Type: Article
Keywords: Carbonate system; Partial pressure of CO2; Carbon cycle; Global model
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.chemgeo.2018.08.010
ISSN: 0009-2541
Projects: PalMod
Date Deposited: 13 May 2020 11:30
Last Modified: 08 Feb 2021 07:40
URI: http://oceanrep.geomar.de/id/eprint/49682

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