Intensified carbonate weathering during storm events in a highly-erosion river catchment

Abstract

Carbonate weathering is sensitive to tectonic and climatic settings due to its rapid dissolution kinetics, playing an important role in the carbon cycle at short time scales (102 to 104 years). Under global warming, extreme weather and hydrological events have become more frequent worldwide. How carbonate weathering and its associated carbon budget respond to these extreme events remains unclear. Here, high-temporal-resolution (weekly) riverine chemistry during 2010 was investigated in the upper Min Jiang, a highly-erosion river catchment on the eastern Tibetan Plateau. River water chemistry during the monsoon season fluctuated with six storm events (9 days in total) that were characterized by 7–14 times higher water discharge and 10–40 times higher erosion than those of the non-monsoon seasons. Based on a forward model, riverine chemistry was dominated by carbonate dissolution in the upper Min Jiang. Compared to the non-monsoon seasons, the storm events triggered 270% and 264% increases in the average fluxes of carbonate weathering and associated CO2 consumption, respectively. Furthermore, an incongruent carbonate dissolution (ICD) model as a possible mechanism was employed to reveal the preferential leaching of Mg2+ and Sr2+ relative to Ca2+ during carbonate weathering under extremely-high erosion at basin scale. Accompanying the ICD, the storm-derived carbonates were likely carried downstream as suspended particles for further weathering. This study demonstrates the intensification of carbonate weathering and a carbon sink by storm events, with incongruent carbonate dissolution under storm-induced high erosion.