Response of the estuarine turbidity maximum to a changing hydrodynamic environment in the Pearl River estuary

Abstract

Suspended particulate matter (SPM) plays an important role in both physical and biogeochemical processes in the estuarine system, and the variation of SPM concentrations have multiple environmental and societal implications. Previous research has shown that gravitational circulation, tidal trapping, sediment resuspension and deposition, and runoff of rivers are the primary controlling factors for the formation of the estuarine turbidity maximum (ETM) in the Pearl River estuary (PRE). However, the mechanistic connection between surface riverine sediment plumes and the ETM, and the spatial and temporal variation of the ETM caused by human-induced morphological change and climate- and land subsidence-induced sea level change remain largely unknown. In our study, Landsat data from the 1970s to 2010s were analyzed to identify the variation of the surface sediment concentration. A 3-Dimensional hydrodynamics-sediment transport model (SCHISM) were used to investigate the impacts of decadal-changes (1970s-2010s) of morphology, riverine sediment discharge and sea level on the spatial and temporal variation of ETM. Sediment trapping mechanisms (e.g. topographic and tidal trapping, estuarine fronts) were investigated for their influence on the variation of the ETM to clarify the nonlinear relationships between various sediment trapping processes and the ETM in the PRE. With this study, we aim to better understand the response of the ETM to past and future environment changes caused by both climate and human activities.