Beyond salt: Effects of estuarine circulation and mixing timescales on biogeochemistry

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Simplified physics using theoretical approaches will allow prediction of the response of coastal environments, particularly their water quality, to climate variations. This study will attempt to derive reliable results from simplified physics that are equivalent to results from complex three-dimensional computer models in estuaries, based on full-fledged physics principles. The study will then incorporate biogeochemical variables, such as carbon and dissolved oxygen, in the theoretical formulation and explore different responses of an estuary to processes that can be linked to climate variability. This project will support one graduate student and its results will benefit regional stakeholders such as fishery and aquaculture managers, state agencies and indigenous people.The goals of this study are twofold: 1) to advance understanding of the link between vertical mixing and horizontal advection in estuaries, and 2) to investigate the effects of transport timescales and spatial structure on biogeochemical properties in estuaries. The investigation will extrapolate the efflux-reflux theory of Cokelet & Stewart (1985), showing that horizontal exchange transports are comparable to vertical transports. The approach is to apply the theory to the output from idealized and realistic numerical models. Particle-tracking experiments will further determine which portion of the water is brought into the estuary with the exchange flow and which portion is mixed upward, becoming part of the outflow. The study will also explore a parameter space for various exchange rates, via box models. The project will continue to support one graduate student. Results will eventually be useful for studies of water quality in estuaries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.