Particulate Organic Carbon (POC) is an import reservoir of reduced carbon on Earth. Observational studies have shown that its spatio-temporal distribution at the estuarine-coastal oceans is highly affected by extreme weather events. However, the controlling mechanisms were not clearly elucidated due to limited in-situ and satellite data coverage. In this study, we incorporated carbonate cycle into a previous developed fully coupled ocean-atmospheric-sediment-biogeochemical modelling system for the Pearl River Estuary and adjacent coastal ocean in South China Sea. We quantitatively estimated the POC response to floods and suspended sediment concentration (SSC) variation under the passage of two successive typhoons, Hato and Pakhar (2017). Through scenario experiments, we found that typhoon-induced floodings leads to a higher input of terrestrial organic carbon into Lingding Bay, resulting in higher POC concentrations in the upper and middle regions. However, the POC concentrations decrease in the lower Bay as the floods reduce the residence time of phytoplankton and consequently prevent the production of marine organic carbon. In contrast, typhoon-induced suspended sediment light attenuation significantly impaired the effectiveness of the biological pump and leading to a significant reduction in marine organic carbon. Within Lingding Bay and shallow coastal region, SSC reduced the POC concentrations before, during and after typhoons. In contrast, typhoon-induced SSC increased the POC concentrations within deep coastal region two-weeks after typhoon passes due to the improved light conditions and unabsorbed nutrients transport offshore. The simulation methods employed in this study can be applied to other estuarine-coastal systems to better quantitatively analyzing carbon cycle and transport under extreme weather conditions in the context of Land-Ocean-Aquatic Continuum (LOAC).


 

typhoon, carbon cycle, particulate organic carbon, Pearl River Estuary-Coastal Ocean system