The Brine Zone in the McMurdo Ice Shelf, Antarctica

• Main Authors: Kovacs, Austin, Gow, Anthony J, Cragin, James H, Morey, Rexford M
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1982
• Subjects: Physical and Dynamic Oceanography; Snow; Ice and Permafrost; *ANTARCTIC REGIONS; *BOUNDARIES; *BRINES; *ICE PENETRATION; *SEA WATER; CHEMICAL ANALYSIS; CORE SAMPLING; DENSITY; ECHO RANGING; LEADING EDGES; MEASUREMENT; MIGRATION; PROFILES; RANGE(DISTANCE); SALINITY; SEA ICE; TABLES(DATA); *MCMURDO ICE SHELF; Antarctic; McMurdo Ice Shelf; Antarc*; Antarctica; Ice; Ice Shelf; permafrost; Sea ice
• Online Access: http://www.dtic.mil/docs/citations/ADA124516; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA124516

Observations of a 4.4-m-high brine step in the McMurdo Ice Shelf, Antarctica, show that it has migrated about 1.2 km in 4 years. The present brine wave is overriding an older brine-soaked layer. This migration is proof of the dynamic nature of the step, which is the leading edge of a brine wave that originated at the shelf edge after a major break-out of the McMurdo Ice Shelf. The inland boundary of brine penetration is characterized by a series of descending steps that are believed to represent terminal positions of separate intrusions of brine of similar origin. The inland boundary of brine percolation is probably controlled largely by the depth at which brine encounters the firn/ ice transition (43 m). However, this boundary is not fixed by permeability considerations alone, since measurable movement of brine is still occurring at the inland boundary. Freeze-fractionation of the seawater as it migrates throught the ice shelf preferentially precipitates virtually all sodium sulfate, and concomitant removal of water by freezing in the pore spaces of the infiltrated firm produces residual brines approximately six times more concentrated than the original seawater.