A quantitative method for deriving salinity of subglacial water using ground-based transient electromagnetics

Liquid water can exist at temperatures well below freezing beneath glaciers and ice sheets, where subglacial water systems, fresh and saline, have been shown to host unique microbial ecosystems. Geophysical techniques sensitive to fluid-content contrasts, e.g. electromagnetics, can characterize subg...

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Bibliographic Details
Published in:Journal of glaciology Vol. 68; no. 268; pp. 319 - 336
Main Authors: Killingbeck, Siobhan F., Dow, Christine F., Unsworth, Martyn J.
Format: Journal Article
Language:English
Published: Cambridge, UK Cambridge University Press 01.04.2022
Subjects:
Algorithms
Bayesian analysis
Cold
Depth
Electrical resistivity
Electromagnetic radiation
Feasibility studies
Freezing
Geophysical methods
Glaciation
Glaciers
Groundwater
Hydrology
Ice
Ice sheets
Ice thickness
Lakes
Mathematical models
Microorganisms
Probability theory
Radar
Radar data
Saline water
Salinity
Salinity effects
Sediments
Seismic data
Seismological data
subglacial lake
Subglacial lakes
Subglacial water
transient electromagnetics
Water
Antarctica
subglacial water
transient electromagnetics
subglacial lake
Salinity
ISSN:0022-1430, 1727-5652
Online Access:Get full text
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Summary:Liquid water can exist at temperatures well below freezing beneath glaciers and ice sheets, where subglacial water systems, fresh and saline, have been shown to host unique microbial ecosystems. Geophysical techniques sensitive to fluid-content contrasts, e.g. electromagnetics, can characterize subglacial water and its salinity. Here, we assess the ground-based transient electromagnetic (TEM) method for deriving the resistivity and salinity of subglacial water. We adapt an existing open-source Bayesian inversion algorithm, which uses independent depth constraints, to output posterior distributions of resistivity and pore fluid salinity with depth. A variety of synthetic models, including a thin (5 m), conductive (0.16 Ωm), hypersaline (147 psu) subglacial lake, are used to evaluate the TEM method for imaging under 800 m-thick ice. The study demonstrates that TEM methods can resolve conductive, saline bodies accurately using external depth constraints, for example, from radar or seismic data. The depth resolution of TEM can be limited beneath deep (>800 m), thick (>50 m) conductive, water bodies and additional constraints from passive electromagnetic (EM) methods could be used to reduce ambiguities in the TEM results. Subsequently, non-invasive active and passive EM methods could provide profound insights into remote aqueous systems under glaciers and ice sheets.
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ISSN:0022-1430
1727-5652
DOI:10.1017/jog.2021.94