zone of ablation

On a glacier, the zone of ablation or zone of wastage is the area in which annual loss of snow through melting, evaporation, iceberg calving and sublimation exceeds annual gain of snow and ice on the surface. Of these, melting is most important in most glaciers, but the others, especially iceberg calving, can be significant. Spatially, the zone of ablation can be identified as the part of the glacier below the snowline. The ablation zone often contains meltwater features such as supraglacial, englacial and subglacial streams. It is also an area where much sediment is deposited at the fringes of the glacier. Ablation in a glacier is a key part of the glacier mass balance.
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The part of a glacier in which there is greater over all loss than gain in volume. A zone of ablation can be identified in the summer by an expanse of bare ice. See also zone of accumulation