Date of Award

2016

Document Type

Open Access Dissertation

Department

Earth and Ocean Sciences

Sub-Department

College of Arts and Sciences

First Advisor

Alicia Wilson

Abstract

Submarine groundwater discharge (SGD) rivals riverine discharge to the world’s oceans but remains poorly understood. Until the early 1990’s, geochemical budgets for the ocean were developed using material fluxes from rivers only. SGD has been shown to carry high concentrations of dissolved nutrients, metals and carbon. However, SGD is a difficult to measure, complex phenomenon driven by multiple physical processes. Groundwater flow and the resultant chemical exchange at the land-sea interface are heavily impacted by the hydrodynamic effects of mixing between variable-density fluids. In order to better understand SGD, investigations have focused on the configuration of the freshwater-saltwater interface in coastal aquifers. This dissertation contributes to the field by providing detailed study of the interplay between the freshwater-saltwater interface and SGD at multiple spatial scales. The first study in this dissertation examines the dynamics of the freshwater-saltwater interface and associated rates of tidally driven and density driven recirculation at the nearshore scale in theoretical beaches. I show that beach slope is an important control on the development of the upper saline plume and therefore associated rates of seawater recirculation and SGD. The second study focuses on SGD, seawater recirculation, and the configuration of the freshwater-saltwater interface in a beach on a transgressive barrier island in Georgia. I show that the inclusion of real-world heterogeneity in a beach groundwater model leads to important deviations from predictions made using only theoretical, homogenous beaches. The third and final study of this dissertation investigates SGD and the freshwater-saltwater interface at Hobcaw Barony, South Carolina. I develop a conceptual model for groundwater flow at the combined nearshore-embayment scale and test the response of these systems to predicted rates of future sea-level rise. I show that SGD and solute transport at these two scales are largely independent, and that the impacts of future sea-level rise will be much more significant for the nearshore scale. Finally, this dissertation aims to provide a comprehensive, spatially-integrated understanding of the pertinent driving forces for coastal groundwater flow and solute transport to aid future studies and management decisions.

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Geology Commons

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