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Hunter, L.E., 1994

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Bibliographic Reference

Hunter, L.E., 1994, Grounding-line systems and glacier mass balance of modern temperate glaciers and their effect on glacier stability: DeKalb, Illinois, Northern Illinois University, Ph.D. dissertation, 499 p., illust.

Abstract

Morainal bank sediment dynamics affect tidewater terminus stability by controlling grounding-line water depth and calving speed termini dynamics to decouple from climatic forcing. Data presented in this study document regional climatic forcing, termini, and ice-proximal sediment dynamics. Investigation of climatic forcing indicates that previous suggestions of climate processes are oversimplified. A preliminary study of climatic patterns suggests that glacier nourishment is from two sources: Middle tropospheric system influences upper neves and the Aleutian Low influences elevations below 2,000 m. The Fairweather Range forms a barrier that causes storms moving off the Gulf of Alaska to deflect toward Cross Sound, causing a southerly introduction of moisture into Glacier Bay. Recent termini fluctuations have been influenced by fjord geometry, morainal bank sedimentation, and iceberg calving. Grand Pacific Glacier exhibits the lowest mass balance indices observed; however, it has overridden its morainal bank in response to changes in tributary ice flux. Margerie Glacier advance has been limited by sediment dynamics beyond the sill of its trough despite a positive mass balance. Retreat of Muir Glacier into a narrow segment of Muir Inlet has allowed the ice flux to balance the calving flux, forming a phase of quasi-stability that has been followed by the most rapid period of fjord infilling ever monitored. Glacial debris fluxes in GBNPP are among the highest ever recorded, with erosion rates ranging from 40.5 to 113.8 mm/yr. Glacial debris flux is controlled by glacier flux rates, valley geometry, bedrock and weathering state, substrate, and glacier thermal regime. Glacifluvial sediment production comprises 83.6 to 98.6 percent of the total glacial sediment production. A sedimentary process hierarchy was determined by monitoring sediment volumes. Glacifluvial dumping and mass movements are first-order processes that add or remove 10{6-7} m3/yr of sediment. Second-order processes (squeeze/push and plume settling), third-order process (conveyor-belt recycling), and fourth-order processes (calve dumping and ice-cliff meltout) introduce 10{5-6}, 10{4-5}, 10{3-4} m3/yr, respectively. Processes that cause morainal bank aggradation (all except mass movements) reduce grounding-line water depth and form a positive feedback on terminus stability.

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