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Definition:
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Dense glacier ice with a blue appearance accounted for by lack of air bubbles. The crystal structure absorbs all colours except the blue part of the visible spectrum. Strictly, blue ice is ice that has originated by recrystallization upglacier and, having followed a trajectory through the interior of the glacier, becomes exposed at the surface downglacier, a locally zero or negative surface mass balance being implied. The term is used loosely, however, to refer to all exposed ice on the Antarctic Ice Sheet; again, the absence of snow and firn implies a locally negative surface mass balance.
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