Supraglacial Stream Dynamics on the Juneau Icefield

ABSTRACT Measurements of discharge, reach morphology, and cross-section morphology in supraglacial streams on the Juneau Icefield reveal controlling variables that have analogous counterparts in alluvial streams. Downward sky radiation imparts a strong diurnal pattern to supraglacial runoff generated by saturated slush flows, precipitation and melting, channel erossion, and spillover from water-filled moulins, crevasses, and supraglacial lakes. Supraglacial streams are generated when runoff is concentrated on glacier slopes and rates of incision exceed rates of glacier surface ablation. Streams leave the surface via moulins and crevasses where the water becomes part of the englacial and subglacial drainage systems. Meander systems develop and migrate downstream, driven by thermal erosion with heat supplied by climatic and hydrologic sources. Sinuosity attains a maximum value, in the absence of other roughness factors, when high stream power is imposed from an adjacent upstream reach. Form-process relation...

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