Radio Echo Sounding: Brine Percolation Layer

Clough, John W.

doi:10.1017/s0022143000022796

Cited by 22 publications

(20 citation statements)

References 2 publications

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“…The light‐snow corridor between White Island and Hut Point suggests that the snow accumulation pattern is locked to the surrounded geography, possibly by a topographically controlled local climate. Such a permanent feature would explain why surveys of the eastern brine boundary did not identify substantial displacements over the last decades [ Clough , ; Kovacs et al , ; Morse and Waddington , ]. The only detected brine migration is a ∼800 m inland propagation (out of our horizontal resolution) from 1977 to 1993 that occurred north and east of Williams Field [ Morse and Waddington , ], matching the area where we estimate the brine to infiltrate the firn‐IV likely by dissolution and/or snow load‐driven compaction.…”

Section: Discussionsupporting

confidence: 63%

Radar detection of the brine extent at McMurdo Ice Shelf, Antarctica, and its control by snow accumulation

Grima

Greenbaum

Garcia

et al. 2016

Geophysical Research Letters

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We derive the surface density and brine infiltration depth/extent at McMurdo Ice Shelf, Antarctica, from combined analysis of radar profiles and radar statistical reconnaissance of the surface from 2011 to 2012 austral summer airborne observations. Most of the brine boundaries appear controlled, directly or indirectly, by the snow accumulation pattern. The infiltration is bounded westward by an ablation area and resides just above the pore close‐off depth over most of its extent. The eastern brine limit matches a light‐snow corridor, suggesting a reversed pressure gradient at depth that might sharply slow down the infiltration. Brine into ice is confirmed at the deepest locations north and east of Williams Field. The ice‐ocean interface is undetected west of the infiltrated zone, except in localized patches. We hypothesize this echo‐free zone to be due to high scattering below the surface, possibly from a network of accreted ice and/or ice platelets at the ice‐ocean interface.

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Section: Discussionsupporting

confidence: 63%

Radar detection of the brine extent at McMurdo Ice Shelf, Antarctica, and its control by snow accumulation

Grima

Greenbaum

Garcia

et al. 2016

Geophysical Research Letters

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“…The radar profiler is capable of monitoring the lateral extent of the brine zone. According toClough [1973] this zone terminates rather abruptly;Figure 4clearly shows, in some detail, the actual configuration of the brine zone at its inland boundary.Internal structure.Discontinuities within the firn can also be detected with the profiler. An example is shown inFigure 3, where the internal layering seems to have been deformed into long-period rolls as a result of the ice shelf pushing against Hut Point Peninsula.…”

mentioning

confidence: 61%

“…To the south and east of Hut Point Peninsula, the shelf is characterized by the widespread occurrence of brine-soaked firn, and data from pits and holes drilled at a few widely scattered locations indicate that brine infiltration extends for a distance of 10-20 km back from the seaward edge of the ice shelf. Only recently have the inland limits of brine penetration for part of the ice shelf been approximately delineated by radio echo sounding [Clough, 1973]. Data from a number of deep holes drilled by R. Paige (personal communication, 1971), in conjunction with the surface and subsurface observations of Heine [1968], seem also to indicate that brine infiltration is accompanied by bottom melting and that the ice shelf thins drastically as it flows toward Hut Point Peninsula.…”

Section: Mcmurdomentioning

confidence: 99%

Brine infiltration in the McMurdo Ice Shelf, McMurdo Sound, Antarctica

Kovacs¹,

Gow²

1975

J. Geophys. Res.

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In recent trials near Hut Point Peninsula an impulse radar profiler was used successfully to monitor the depth characteristics and lateral extent of brine soaking in the McMurdo Ice Shelf. The success of the profiler can be attributed in large part to the significant difference in dielectric properties of dry firn and firn that has become brine soaked by infiltrating seawater. In addition to furnishing a continuous trace of the top of the brine layer, the impulse radar profiler has also revealed the existence of cracks, relict brine horizons, and deformational features within the ice shelf. Data tend to favor lateral infiltration of seawater, either through the seaward edge of the ice shelf or via tensile cracks at the bottom of the ice shelf.

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“…GPR and radio-echo sounding (RES) have been used previously on the Ross Ice Shelf in the McMurdo Station vicinity (Clough, 1973;Gow, 1975, 1977a, b;Kovacs et al, 1982) and in other ice shelf locations far removed from McMurdo (Jezek, 1980;Morey and Kovacs, 1982). The GPR work by Kovacs and Gow and Kovacs et al profiled the migration of brine from the front of the ice shelf into the snow accumulation zone east of the Pegasus site.…”

Section: Introductionmentioning

confidence: 99%

High resolution of glacial ice stratigraphy: A ground‐penetrating radar study of Pegasus Runway, McMurdo Station, Antarctica

Arcone

1996

GEOPHYSICS

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Ground-penetrating radar (GPR) has been used to detect areas of present or potential structural weakness beneath a 3.2-km snow-covered ice runway on the Ross Ice Shelf, Antarctica. The bandwidths of the transmitted wavelets were centered near 500 MHz. The data show many horizons up to tens of meters long and occurring to about a 9-m depth, below which a brine intrusion limits penetration. The horizons are interpreted as discrete scatterers because of their diffraction nature and loss of higher frequencies with depth. The presence of porous ice or dispersed water is interpreted from wavelet phase. The water may be associated with apparent deepening and fading of the brine horizon. If the above interpretation is correct, water occurs at depths to 3.5 m and extends as much as 40 m horizontally, which is greater and deeper than known previously. At 3.5 m depth, the water may be adsorbed on mineral particles rather than remain free. Migration of the diffractions with a singlelayer migration scheme shows all horizons above the brine layer to be small dielectric perturbations within the ice. Stacking and Hilbert transformation of the data reveal slight folding along the length of the runway. Loss of high-frequency amplitude in the wavelets suggests that higher frequency radar might improve resolution only in the top few meters.

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Radio Echo Sounding: Brine Percolation Layer

Abstract: An abrupt change in radio echo sounding travel time was observed on the ice shelf near McMurdo station, Antarctica, and was mapped by a zig-zag traverse. This boundary corresponds to the horizontal extent of brine penetration into the edge of the ice shelf.

Cited by 22 publications

References 2 publications

Radar detection of the brine extent at McMurdo Ice Shelf, Antarctica, and its control by snow accumulation

Radar detection of the brine extent at McMurdo Ice Shelf, Antarctica, and its control by snow accumulation

Brine infiltration in the McMurdo Ice Shelf, McMurdo Sound, Antarctica

High resolution of glacial ice stratigraphy: A ground‐penetrating radar study of Pegasus Runway, McMurdo Station, Antarctica

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