Impact of Typhoons Hato and Pakhar (2017) on Particulate Organic Carbon Transport in the Pearl River Estuary, China: A Numerical Study

Abstract

Estuaries play a crucial role in the transport and cycling of particulate organic carbon (POC) from terrestrial ecosystems to the ocean. However, an understanding of the processes controlling POC dynamics under extreme weather conditions is still lacking. In this study, we established a high‐resolution, coupled atmosphere–ocean–biogeochemistry modeling system for the Pearl River Estuary to investigate the mechanisms controlling POC dynamics during a strong successive typhoon event (Hato and Pakhar, 2017). Our simulation results show that before the typhoons, the POC distribution was characterized by two distinct maxima, sustained by terrestrial inputs and marine production, respectively. However, during the typhoons, strong hydrodynamic conditions and reduced light availability suppressed local primary production, leading to an increase in the dominance of terrestrial POC. In Lingding Bay (LB) and the Western Four Outlets (WFO), POC was mainly supported by regenerated production, whereas in the shallow coastal region (SCR) outside the estuarine, new and regenerated production played an equal role. Regarding POC sinks, zooplankton excretion served as the dominant sink in the outer LB and SCR regions, while sediment denitrification played an equally significant role in the inner LB and WFO. Budget analysis revealed that although the estuary acted as a weak carbon source on an annual basis, successive typhoons can transform it into a weak carbon sink. Our simulation provides novel insights into the impact of extreme weather on POC within estuaries, benefiting the maintenance of ecological health and the development of effective water quality management strategies under global warming.