Remapping programs on glaciers are undertaken to determine changes in ice thickness and volume, which supposedly reflect glacier response to changing climate. However, thickness changes, derived photogrammetrically, cannot be used to determine ablation or other specific mass budget quantities, or response characteristics, without concurrent measurements made on. the glacier surface, The varied nature of the difficulty is illustrated by the following examples: (1) data front South Cascade Glacier demonstrate that the rate of change of thickness is the vectorial combination of emergence velocity, specific net budget rate, and (in the accumulation area only) a compaction velocity; (2) limitations on the use of photogrammetric data to detect and interpret kinematic waves are illustrated by results from Nisqually Glacier; (3) changes in two lobes of Klawatti Glacier show that climatic changes cannot be extrapolated from single-glacier maps because of meso-scale meteorological complications.

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