Author(s): David Dempsey; Pat Langhorne
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Abstract: Much of the coastline of Antarctica is bounded by ice shelves, which influence the coastal sea ice by processes occurring in the ocean cavity at their base. Theoretical studies est imate that basal meltwater may contr ibute as much as 0.2 m to the sea ice thickness over significant portions of the sea ice cover. In particular supercooled water, formed as a result of interact ion with the ice shelf, acts as a heat sink in which ice crystals can nucleate and grow. These crystals, called frazil or platelet ice, accumulate in loose, porous layers beneath the ice cover, and become incorporated into the fabric of the sea ice. In order to gain insight into the details of these crystallographic processes and their contribut ion to the thickness of the sea ice, we have used a 3-dimensional numerical model to simulate the mechanics of the sub-ice platelet layer format ion through the arrival of loose platelet crystals from the water column. This layer is subsequent ly incorporated by thickening of the overlying ice sheet, producing incorporated platelet ice. In addit ion a partial reconstruction of the 3-dimensional incorporated platelet ice structure is used to observe interactions along crystal boundaries. This information is combined with visual observations of loose platelet crystals in the water column and the predictions of the numerical model to develop a more detailed picture of the growth environment beneath the sea ice cover.
Year: 2010