The fate of submarine fresh groundwater reservoirs at the New Jersey shelf, USA

Thomas, Ariel; Reiche, Sönke; Riedel, Marko; Clauser, Christoph

doi:10.1007/s10040-019-01997-y

Cited by 19 publications

(37 citation statements)

References 65 publications

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“…There are three primary challenges in numerically simulating OFG systems. First, there is considerable uncertainty in assigning petrophysical properties such as permeability, sediment compressibility, and porosity offshore (Thomas et al, 2019). Approaches for geologic property modeling in OFG systems can be either deterministic or geostatistical.…”

Section: Investigating Ofg Systemsmentioning

confidence: 99%

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Offshore Freshened Groundwater in Continental Margins

Micallef

Person

Berndt

et al. 2021

Reviews of Geophysics

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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 analyze it to establish the general characteristics and controlling factors. We also assess methods used to map and characterize OFG, identify major knowledge gaps, and propose strategies to address them. OFG has a global volume of 1 × 10 6 km 3 ; 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, salinization 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 profiling, electromagnetic surveying, and numerical 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 modeling, are necessary to assess the potential use of OFG as an unconventional source of water and its role in sub-seafloor geomicrobiology. Plain Language Summary This review paper considers offshore freshened groundwater (OFG), which is water hosted in sediments and rocks below the seafloor, with a total dissolved solid concentration lower than seawater. We have compiled >300 records to demonstrate that freshened groundwater occurs offshore on most continents around the world and has a global volume of 1 × 10 6 km 3. The majority of OFG was deposited when sea level was lower than today and is hosted in sandy sub-seafloor layers that are located within 55 km of coasts in water depths less than 100 m. We present a range of geochemical, geophysical, and modeling approaches that have successfully been used to investigate OFG systems. We also propose approaches to address key scientific questions related to OFG, including whether it may be used as an unconventional source of potable water in coastal areas.

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Section: Investigating Ofg Systemsmentioning

confidence: 99%

“…The blue line presents the mean simulated salinity profile while the black line denotes observed conditions from IODP Expedition 313 Wells M0027, M0028, and M0029. Modified from Thomas et al (2019).…”

Section: Investigating Ofg Systemsmentioning

confidence: 99%

Offshore Freshened Groundwater in Continental Margins

Micallef

Person

Berndt

et al. 2021

Reviews of Geophysics

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“…(B) Cosine of phase attribute with major systems tracts boundaries (including sequence boundaries and transgressive surfaces/maximum regression surfaces) labelled to highlight the correlation of key seismic sequence stratigraphic relationships. (C) Original systems tracts interpretation by Reference [70] overlain on seismic data. (D) Stochastically generated facies distribution.…”

Section: Seismic Morpho-structural Interpretationmentioning

confidence: 99%

“…Figure2. Example of use of seismic stratigraphic and attribute analysis for lithology/facies prediction in groundwater research (modified after Reference[70]). (A) Amplitude of a seismic line across the New Jersey continental shelf (see case study in Section 3.1.1 of this paper).…”

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confidence: 99%

Seismic Reflection Methods in Offshore Groundwater Research

et al. 2020

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There is growing evidence that passive margin sediments in offshore settings host large volumes of fresh and brackish water of meteoric origin in submarine sub-surface reservoirs. Marine geophysical methods, in particular seismic reflection data, can help characterize offshore hydrogeological systems and yet the existing global database of industrial basin wide surveys remains untapped in this context. In this paper we highlight the importance of these data in groundwater exploration, by reviewing existing studies that apply physical stratigraphy and morpho-structural interpretation techniques to provide important information on—reservoir (aquifer) properties and architecture, permeability barriers, paleo-continental environments, sea-level changes and shift of coastal facies through time and conduits for water flow. We then evaluate the scientific and applied relevance of such methodology within a holistic workflow for offshore groundwater research.

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“…Recent analytical and SEAWAT (Langevin et al, 2008) modeling studies underline the importance of heterogenic geological conditions (mainly presence and extension of aquitards) on potential OFGV occurrence (Van Engelen et al, 2018;Knight et al, 2018;Morgan et al, 2018;Solórzano-Rivas and Werner, 2018), turning away from earlier simulations embedding homogeneous geological conditions (Ranjan et al, 2009;Michael et al, 2013;Werner et al, 2013;Ketabchi et al, 2016) and moving toward more complex heterogeneous subsurface representation (e.g., Michael et al, 2016;Zamrsky et al, 2018;Thomas et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Geological Heterogeneity of Coastal Unconsolidated Groundwater Systems Worldwide and Its Influence on Offshore Fresh Groundwater Occurrence

et al. 2020

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Numerous coastal areas worldwide already experience fresh water shortages due to overexploitation and salt water intrusion. Future climate change and population growth will further intensify this threat in more areas in coming decades. Therefore, it is necessary to explore any potential fresh water source, such as offshore fresh groundwater, that could alleviate this fresh water shortage and provide valuable time for adaptation measures implementation and changes in water management strategies. Recent evidence suggests that a disproportionally large portion of human population living in coastal areas relies on groundwater resources stored in underlying unconsolidated groundwater systems. These systems are often very heterogeneous, combining numerous high permeability aquifers interlaid with low permeability aquitards with varying total thickness. This heterogeneity is a major control on the fresh groundwater volume and groundwater salinity distribution within such systems. Thus, the quantification of geological heterogeneity is often the limiting factor when estimating fresh groundwater volumes, both inland and offshore, along the global coastline. To overcome this obstacle, we combine conceptual geological models with available state-of-the-art global datasets to derive a set of geological heterogeneity parameter distributions quantifying geological heterogeneity of coastal unconsolidated groundwater systems (CUGSs) as formed over last 1 Ma. These are then used in an algorithm designed to build synthetic heterogenic parameterizations of CUGSs along the global coastline. These, in turn, provide key input for modeling variabledensity groundwater flow and coupled salt transport to analyze changes in groundwater salinities and offshore fresh groundwater volume (OFGV). Such an analysis is performed over one full glacial-interglacial cycle (the last 0.13 Ma) to account for oscillating sealevel conditions and shifts in coast-line positions and salinity incursions. Our simulation results show a close match between the modeling scenarios and values presented by literature sources demonstrating the potential of the hereby presented methodology to be applied in similar future studies.

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The fate of submarine fresh groundwater reservoirs at the New Jersey shelf, USA

Cited by 19 publications

References 65 publications

Offshore Freshened Groundwater in Continental Margins

Offshore Freshened Groundwater in Continental Margins

Seismic Reflection Methods in Offshore Groundwater Research

Geological Heterogeneity of Coastal Unconsolidated Groundwater Systems Worldwide and Its Influence on Offshore Fresh Groundwater Occurrence

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