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

Abstract

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.

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

“…It may be that horizontal stresses have altered permeability and forced a concentration of brine at this point. Diffraction evidence for cracking in the accumulation zone has been noted by Kovacs and Gow (1975).…”

“…The strongest feature in all these profiles is the horizon between 8 and 9 m depth. We believe this is brine because it has been profiled continuously into the accumulation zone (Arcone et al, 1994) where it has been positively identified (Kovacs and Gow, 1975) by drilling (alternatively this horizon could be accreted sea ice beneath Pegasus (A. J. Gow, pers. comm.).…”

“…The brine may be intruding into porous ice, but we do not have deep enough cores to confirm this. Kovacs and Gow (1975) refer to its event on their radar profiles of the accumulation zone as the "brine layer," as they point out that brine cannot penetrate snow or ice with density greater than about 0.8. However, Kovacs et al (1982) later found that this is not entirely true and reviewed the work of others on possible infiltration mechanisms.…”

Chemical Fractionation of Brine in the McMurdo Ice Shelf, Antarctica

“…Sea-water infiltration into porous ice shelves has been observed at a number of Antarctic locations (Dubrovin, 1962;Yevteyev, 1962;Stuart and Bull, 1963;Heine, 1968;Thomas, 1975;Gow, 1975, 1977;Kovacs and others, 1982[aJ). Much of the past work has focused on either determining the geographical extent of the brine penetration inland using radio echo-sounding techniques (CIough, 1973;Kovacs and Gow, 1975) or on studying iceshelf brine thermodynamics (Thomas, 1975 layer formation was believed to be due to vertical infiltration of sea-water into porous firn (Stuart and Bull, 1963) but Risk and Hochstein (I967), and Kov::.cs and Gow (I975), have concluded from their observations on the McMurdo Ice Shelf that lateral infiltration of sea-water from the ice-shelf edge is the dominant mechanism of brine infiltration. More recent observations by Kovacs and others (l982[b J) show that lateral infiltration is itself dominated by wave-like intrusions of sea-water triggered by periodic break-out (calving) of the ice front in McMurdo Sound.…”

Thickness and Structure of Antarctic Sea Ice Measured by Drilling and Impulse Radar

“…Physical and electromagnetic properties of sea ice were characterized by data analyzed from cores drilled at several points on the surface of a firn layer on an ice shelf Morey 1979, Kovacs andGow 1975). The thickness of the sea ice was profiled by direct measurements of the drilled cores, and also by a remote sensing technique using an impulse radar system which conducted continuous sounding onto this surface from which profiling was possible.…”