Offshore freshened groundwater in continental margins.

Micallef, Aaron , Person, Mark, Berndt, Christian , Bertoni, Claudia, Cohen, Denis, Dugan, Brandon, Evans, Rob, Haroon, Amir , Hensen, Christian , Jegen, Marion , Key, Kerry, Kooi, Henk, Liebetrau, Volker, Lofi, Johanna, Mailloux, Brian J., Martin‐Nagle, Renée, Michael, Holly A., Müller, Thomas , Schmidt, Mark , Schwalenberg, Katrin, Trembath‐Reichert, Elizabeth, Weymer, Bradley , Zhang, Yipeng and Thomas, Ariel T. (2021) Offshore freshened groundwater in continental margins. Open Access Reviews of Geophysics, 59 (1). Art.Nr. e2020RG000706. DOI 10.1029/2020RG000706.

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Supplementary data:


First reported in the 1960s, offshore freshened groundwater (OFG) has now been documented in most continental margins around the world. In this review we compile a database documenting OFG occurrences and analyse it to establish the general characteristics and controlling factors. We also assess methods used to map and characterise OFG, identify major knowledge gaps and propose strategies to address them. OFG has a global volume of 1 million km3; it predominantly occurs within 55 km of the coast and down to a water depth of 100 m. OFG is mainly hosted within siliciclastic aquifers on passive margins and recharged by meteoric water during Pleistocene sea‐level lowstands. Key factors influencing OFG distribution are topography‐driven flow, salinisation via haline convection, permeability contrasts, and the continuity/connectivity of permeable and confining strata. Geochemical and stable isotope measurements of pore waters from boreholes have provided insights into OFG emplacement mechanisms, while recent advances in seismic reflection, electromagnetic surveys and mathematical models have improved our understanding of OFG geometry and controls. Key knowledge gaps, such as the extent and function of OFG, and the timing of their emplacement, can be addressed by the application of isotopic age tracers, joint inversion of electromagnetic and seismic reflection data, and development of three‐dimensional hydrological models. We show that such advances, combined with site‐specific modelling, are necessary to assess the potential use of OFG as an unconventional source of water and its role in sub‐seafloor geomicrobiology.

Document Type: Article
Keywords: offshore freshened groundwater, continental margin, marine hydrogeology, geochemistry, geophysics, modelling
Research affiliation: HGF-UFZ
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Woods Hole
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Main POF Topic: PT8: Georesources
Refereed: Yes
Open Access Journal?: No
Publisher: AGU (American Geophysical Union), Wiley
Date Deposited: 26 Nov 2020 13:58
Last Modified: 07 Feb 2024 15:28

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