Decomposing ETM Dynamics in an Energetic Estuary
Jesse Lopez, Oregon Health and Science University
Situated along the Pacific coast of the Northwest United States, the Columbia River estuary features at least two estuarine turbidity maxima (ETM), or regions characterized by high concentrations of sediments. These ETM are important biogeochemical “hotspots” that contribute to many of the ecosystem services of the estuary. As part of a broader effort to model biogeochemical processes, we present the results of a numerical sediment model calibrated to the Columbia River estuary to study sediment dynamics. In particular, we investigate the physical processes leading to the generation of the ETM, including gravitational circulation, tidal asymmetry, and the settling and resuspension of particles. We estimate the importance of each process by comparing the magnitude and timing of ETM events in each numerical simulation against those from a baseline run in both quasi-realistic open channels and realistic domains. Preliminary results suggest that the Columbia River ETM can be created without settling processes, relying only on, in order of importance, the trapping processes of gravitational circulation, tidal asymmetry, and particle resuspension due to erosion. These results contribute to our understanding of the precise processes governing sediment dynamics in the Columbia River estuary and constitute a small, but important step in the development of a full-fledged biogeochemical model.
Abstract Author(s): Jesse Lopez, Antonio Baptista