| Summary: | Most δ18O values of samples from the principal river are within the range -12.5 to -14.0‰. Because new snow tends to be relatively depeleted of δ18O, water leaving the glacier early in the summer has low δ18O values. Subsequently, values rise as contributions of old snow, glacier ice, and their melt waters, which are isotopically heavier (median δ18O values generally above -12.0‰) dilute the δ18O-depleted base-flow. Towards the end of the summer, as surface melting declines, δ18O values tend to fall. Between-year differences of within-summer trends reflect differences of development of the glacier's drainage systems. The drainage systems are affected by outbursts from a glacier-dammed lake. During fine weather, δ18O variations follow the diurnal cycle of surface melting: they are strongly correlated with, but lag behind, air temperatures. -from Author
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