Author(s): Alexander J. Gough; Andrew Mahoney; Pat Langhorne; Mike Williams; Tim Haskell
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Abstract: Sea ice with a negative freeboard is common around Antarctica, both in the pack and in the fast ice close to ice shelves where wind-blown snow from the continent accumulates. Under the right conditions, the depressed ice surface floods with sea water and the resulting slush can refreeze to form snow ice. This may form a substantial fraction of the sea ice, especially in heavily snow loaded multiyear fast ice. The mechanical strength of snow ice is important as this ice type frequently buttresses ice shelves, and often occurs in areas critical to the operation of research stations. The process of sea water flooding and the subsequent fate of brine from a flooded slush layer after refreezing provide insight for models of sea ice desalination. Multiyear sea ice covered the southern portions of McMurdo Sound from 1998 to 2011, a situation that was somewhat unusual in the short history of human occupation. A number of roads, routes and field camps utilize the multi- and first-year sea ice, probably making it the most trafficked sea ice in Antarctica. After a number of years most of the ice thickness was composed of frozen flooded snow. We profiled the thickness variations of an area of ten-year-old sea ice under compression by the nearby McMurdo Ice Shelf. We investigate the bulk mechanical properties of snow ice and put limits on the accumulated strain imposed by the ice shelf. We also provide measurements of sea ice salinity and porosity and use these to speculate on the mode of flooding and their implications for the permeability of sea ice.
Year: 2012