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Definition:
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Loss of mass from a glacier by melting of ice or firn between the summer surface and the bed. See mass-balance units. Internal ablation can occur due to strain heating of temperate ice as the ice deforms. However, the largest heat sources for internal ablation are likely to be the potential energy released by downward motion of the ice and of meltwater. The magnitude of the former is equivalent to a few mm w. E. A-1, and of the latter, which occurs mainly in conduits transferring water from the glacier surface to the bed, to up to a few tens of mm w. E. A-1. (These rates are expressed over the extent of a typical valley glacier.)
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