Brugman, Melinda Mary (1987) Water flow at the base of a surging glacier. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-07192006-093757
Water tracing experiments were successfully conducted over a distance of ten kilometers along the base of Variegated Glacier for the purpose of characterizing the water drainage system of the glacier in the surging as compared to the non-surging state. Three tracing experiments were conducted, and fluorescent dyes, Rhodamine WT and Tinopal AMS, were injected into boreholes at separate locations. The two Rhodamine WT experiments were conducted over a 10 km distance, both during the most rapid surging motion of the glacier, and after its cessation.
In each experiment, the terminus streams were monitored for stream discharge, sediment content and tracer concentration. Rhodamine WT tracer was significantly adsorbed on the suspended sediment, particularly during the surge. The adsorption behavior followed the Langmuir model, and calculated distribution coefficients of Kd = 100 to 1000 ml/g were measured for during the glacier surge. The Kd values measured after the surge were lower than during the surge by a factor of 10 to 1000. The much higher Kd values in the surging as compared to non-surging glacier states can be best explained by a factor of 10 to 1000 decrease in the modal and/or mean grain-size of the suspended sediment. The abundance of fine-grained sediment during the surge is probably due to increased grinding of rock material at the glacier bed.
Theoretical models of tracer dispersion in a single tunnel, were compared to models of dispersion in linked-cavity systems to infer the details of water flow at the glacier bed. The broad, roughly symmetrical, dye-return curve measured during the glacier surge conforms to diffusive dispersion theory, and differs sharply from the highly asymmetrical dispersion curve measured after the surge. Results indicate the dispersion behavior, and calculated Manning roughness, of the post-surge Variegated Glacier is similar to those of glaciers that do not surge. The drainage system of the Variegated Glacier in the surging state is consistent with a model of tracer dispersion in an interconnecting network of conduits and cavities, and is strikingly different from the tunnel system indicated for the non-surging state.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Subject Keywords:||Surge, glacier, water, rapid, galloping, outburst, hydrology, cavity, channels, linked, cavity-conduit, model, mannings, roughness, base, glacier, water , pressure, basal, exponential, storage, fluorescent, dye, Rhodamine, WT, Tinopal, tracking, PPB, sediment, calibration, extraction, turbidity, floculation, methanol, flow, instability, floating, Alaska, Yakutat, survey|
|Degree Grantor:||California Institute of Technology|
|Division:||Geological and Planetary Sciences|
|Major Option:||Geological and Planetary Sciences|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||7 July 1986|
|Non-Caltech Author Email:||mindy.brugman (AT) canada.ca|
|Additional Information:||This thesis section used for defending the PhD thesis was a contribution to the evaluation of a surge type glacier during a major surge. This involved a joint field project with University of Alaska, CalTech, University of Washington and more. These results contributed in an important way to the joint Science paper first authored by Barclay Kamb to explain the Surge Mechanism. The results have applications to surge-type glaciers around the world, that are at the melting point at their beds and involved water delivery physics as their mechanism for flow instability. The results also relate to any medium where flow of water occurs in linked cavity-conduit systems, that can revert to a single organized conduit drainage system. New methods were developed to extract dye from turbid waters. Modeling dye tracing results allowed testing theories of water drainage controls on dispersion through a porous medium. The friction at the base of a glacier and the back up of water which can effectively float a glacier is intimately linked to the character of the drainage channels and cavities at the glacier bed. This thesis provides evidence and explanation for how the surging glacier develops, and why the sliding and seasonal response time is so sensitive to water pressure. Additional thesis research section was prepared on the dynamics of debris laden and the flow response of Shoestring Glacier to the eruption of Mount St Helen's, before and after the 1980 eruption, published in part in the USGS MSH Special Publication on the 1980 eruption. With the combined edited thesis nearly 800 pages we just defended on the Surging Glacier section.|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||11 Aug 2006|
|Last Modified:||22 Oct 2015 22:35|
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