Temporal variations in porewater fluxes to a coastal lagoon driven by wind waves and changes in lagoon water depths

Rodellas, Valenti, Cook, Peter G., McCallum, James, Andrisoa, Aladin, Meule, Samuel, and Stieglitz, Thomas C. (2020) Temporal variations in porewater fluxes to a coastal lagoon driven by wind waves and changes in lagoon water depths. Journal of Hydrology, 581. 124363.

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Abstract

Porewater fluxes, including fresh groundwater discharge and circulation of surface waters through sediments, are increasingly documented to play an important role in hydrological and biogeochemical cycles of coastal water bodies. In most studies, the magnitude of porewater fluxes is inferred from geochemical tracers, but a detailed understanding of the underlying physical forces driving these fluxes remains limited. In this study, we evaluate the mechanisms driving porewater fluxes in the shallow coastal La Palme lagoon (France). We combined measurements of variations of salinity and temperature in the subsurface with 1-dimensional fluid, salt and heat transport models to evaluate the dynamics of porewater fluxes across the sediment-water interface in response to temporally variable forcings. Two main processes were identified as major drivers of porewater fluxes: i) temporal variations of lagoon water depths (forcing porewater fluxes up to 25 cm d(-1)) and ii) locallygenerated wind waves (porewater fluxes of similar to 50 cm d(-1)). These processes operate over different spatial and temporal scales; Wind-driven waves force the shallow circulation of surface lagoon waters through sediments (mostly < 0.2 m), but are restricted to strong wind events (typically lasting for 1-3 days). In contrast, porewater fluxes driven by variations of lagoon water depths flush a much greater depth of sediment (> 1 m). The spatial and temporal scales of driving forces will largely determine the significance of porewater fluxes, as well as their chemical composition. Thus, an appropriate evaluation of the magnitude of porewater-driven solute fluxes and their consequences for coastal ecosystems requires a solid and site-specific understanding of the underlying physical forces.

Item ID: 62556
Item Type: Article (Research - C1)
ISSN: 0022-1694
Keywords: Porewater exchange, Submarine groundwater discharge, Coastal lagoon, Driving forces, Waves, Salinity, Temperature
Copyright Information: (C) 2019 Elsevier B.V. All rights reserved.
Funders: French National Research Agency (ANR), European Union (EU), Catalan Government (CG), Institute of Advanced Studies (IméRA), Aix-Marseille Université
Projects and Grants: ANR-14-ACHN-0007-01, ANR-11-LABEX-0061, ANR-11-IDEX-0001-02, EU Marie Sklodowska-Curie grant agreement no. 748896, CG 017-BP-00334
Date Deposited: 18 Mar 2020 07:30
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology @ 30%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology @ 40%
04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 30%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960903 Coastal and Estuarine Water Management @ 50%
96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 50%
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