Temporal variability of lagoon–sea water exchange and seawater circulation through a Mediterranean barrier beach

Tamborski, Joseph, van Beek, Pieter, Rodellas, Valenti, Monnin, Christophe, Bergsma, Erwin, Stieglitz, Thomas, Heilbrun, Christina, Cochran, J Kirk, Charbonnier, Celine, Anschutz, Pierre, Bejannin, Simon, and Beck, Aaron (2019) Temporal variability of lagoon–sea water exchange and seawater circulation through a Mediterranean barrier beach. Limnology and Oceanography. (In Press)

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Abstract

The subterranean flow of water through sand barriers between coastal lagoons and the sea, driven by a positive hydraulic gradient, is a net new pathway for solute transfer to the sea. On the sea side of sand barriers, seawater circulation in the swash-zone generates a flux of recycled and new solutes. The significance and temporal variability of these vectors to the French Mediterranean Sea is unknown, despite lagoons constituting ~ 50% of the coastline. A one-dimensional 224Raex/223Ra reactive-transport model was used to quantify water flow between a coastal lagoon (La Palme) and the sea over a 6-month period. Horizontal flow between the lagoon and sea decreased from ~ 85 cm d−1 during May 2017 (0.3 m3 d−1 m−1 of shoreline) to ~ 20 cm d−1 in July and was negligible in the summer months thereafter due to a decreasing hydraulic gradient. Seawater circulation in the swash-zone varied from 10 to 52 cm d−1 (0.4–2.1 m3 d−1 m−1), driven by short-term changes in the prevailing wind and wave regimes. Both flow paths supply minor dissolved silica fluxes on the order of ~ 3–10 mmol Si d−1 m−1. Lagoon–sea water exchange supplies a net dissolved inorganic carbon (DIC) flux (320–1100 mmol C d−1 m−1) two orders of magnitude greater than seawater circulation and may impact coastal ocean acidification. The subterranean flow of water through sand barriers represents a significant source of new DIC, and potentially other solutes, to the Mediterranean Sea during high lagoon water-level periods and should be considered in seasonal element budgets.

Item ID: 58638
Item Type: Article (Research - C1)
ISSN: 1939-5590
Copyright Information: © 2019 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography. This is an open access article under the terms of the Creative Commons Attribution License (CC by 4.0), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Funders: French National Research Agency (ANR), FEDER, European Research Council (ERC)
Projects and Grants: ANR-15-CE01-0004; P.v.l, ANR-14-ACHN-0007-01, project medLOC, ANR-11-LABEX-0061, Horizon 2020 (grant 748896)
Date Deposited: 24 Jul 2019 04:53
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 @ 30%
04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 40%
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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