Large invisible carbon sink potential of global clay minerals to mitigate climate change

Abstract

The chemical weathering of clay minerals widely distributed in the soil have great potential of carbon sink (CS), but the magnitude and influence mechanisms of this CS are unclear. Here we analyse recent changes in five major clay minerals (chlorite, smectite, mica, illite, and vermiculite) carbon sink and its driving factors, using a process-based model (PROFILE) and satellite data assimilation. We show that magnitude of CS in five major clay minerals is about 0.11 Pg C yr-1 from 0 to 2m depth of soil, which is one third of CS in rocks and also may be mainly responsible for the world's missing carbon sink. According to our simulations, the linear trend of CS during 1970-2018 showing that CS in 56% of the world increasing significantly, although the intensification of CS cannot be explained by soil moisture (SM) or soil temperature (STMP) alone, they are the dominant cause of the intensification of CS in the high latitude area and the decrease of CS in parts of the tropics, while in areas where SM is drier, STMP may weaken the former’s negative effect on CS. Besides, simulation results based on medium emission scenarios indicating that CS may increase by about 36% by the end of this century. These results highlight that a more comprehensive understanding of the magnitude and driving mechanism of the soil minerals’ CS is the key to realizing their potential as a nature-based climate solution.