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

• Published in: Limnology and Oceanography
• Main Authors: Tamborski, Joseph, Beek, Pieter, Van, Rodellas, Valenti, Monnin, Christophe, Bergsma, Erwin, Anschutz, Pierre, Stieglitz, Thomas, Heilbrun, Christina, Cochran, J. Kirk, Charbonnier, Celine, Bejannin, Simon, Beck, Aaron
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University (JCU), Stony Brook University SUNY (SBU), State University of New York (SUNY), Helmholtz Centre for Ocean Research Kiel (GEOMAR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: lagoons; circulation; submarine groundwater discharge; radium; radon; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Swash; Ocean acidification
• Online Access: https://hal.science/hal-02095578; https://hal.science/hal-02095578/document; https://hal.science/hal-02095578/file/Tamborski_et_al_2018_LnO_Resubmission_CLEAN.pdf; https://doi.org/10.1002/lno.11169

International audience 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.