Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: William Locke. Includes bibliographical references (p. 93-97).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 118-122).

Thesis (Ph. D.)--University of California, Santa Cruz, 2003. / Typescript. Includes bibliographical references (leaves 115-128).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research .pdf file viewed on (June 25, 2007) Includes bibliographical references.

In this thesis, I explore the flow dynamics associated with ice shelves confined within channels and the buttressing they provide to grounded ice. Ice shelves are the floating extensions of ice sheets and act as the interface between the ice sheet and the ocean. They form when ice flows out from the interior of the ice sheet towards the coast and begins to float as the ice thins. Ice shelves are often found within a channel or pinned in place by stationary bedrock outcrops. The interest in their dynamics is motivated by the buttressing effect they provide to the grounded ice, which strongly controls the rate of ice discharge and thereby the contribution to sea-level rise. I use a combination of mathematical modeling, fluid-mechanical laboratory experiments and geophysical data analysis to develop an improved understanding of ice-shelf flow dynamics. Initially, geophysical data in the form of Antarctic ice-surface velocity data is analysed, producing maps of strain rate, shear rate and strain orientation for Antarctic ice shelves. This allows the geophysical setting and flow processes to be explored, particularly by identifying areas where resistance to ice flow is generated and regions of the shelf that make no contribution to buttressing. Using the geophysical data, I find good agreement between a theoretical scaling relationship for ice flow at the ice-shelf calving front and data from Antarctic ice shelves. I proceed to develop an idealized mathematical model of an ice shelf confined to flow in a channel. By assuming shear-dominated dynamics within the shelf, analytical solutions are obtained for steady-state ice-shelf thickness profiles in parallel and diverging channels. This model is developed further to include both shear and extensional stresses, from which numerical solutions for steady-state shelves are calculated. The results from these two models are then compared. It is found that shear stresses dominate the dynamics throughout the majority of the shelf, with adjustment regions at the upstream and downstream boundaries where extensional dynamics become important. Output from these models is also compared with geophysical data and it is observed that there is good agreement between several features of the thickness profiles and velocity fields. In addition to the geophysical data, comparisons are made with fluid-mechanical laboratory experiments designed to simulate the flow of an ice shelf in a channel. The advantage of performing experiments of this kind is that parameters such as the fluid rheology can be varied, allowing for direct comparison with a range of parameters in the mathematical models. From these experiments, surface velocity fields and thickness profiles are collected, which are used to make comparisons with the models. Clear differences are observed in the velocity and strain-rate fields produced using fluids with different rheologies, for which there is qualitative agreement with the output from the mathematical models.

No description available.

The factors affecting the distribution of surge-type glaciers and the causes of the surge mechanism are not fully understood. Statistical analyses of glaciers in Svalbard have been used to identify characteristics which are related to surging. Field experiments were undertaken on Bjuvbreen, a small surge-type glacier in central Spitsbergen, to determine the dynamics and hydrology of the glacier during its quiescent phase. The probability that a glacier in the Svalbard sample population was surge-type was 36·4%. The probability varied spatially within the sample area. Glaciers resting on sedimentary tocks had a greater probability of being surge-type compared to those overlying igneous or metamorphic rocks. The probability of surging was also increased in glaciers with a two-layered thermal structure as indicated by radio echo sounding. Geometrical characteristics such as slope, orientation, curvature and the presence of tributaries were not related to surge-type behaviour, although long glaciers had a greater chance of being surge-type. Certain aspects of Kamb's and Fowler's theories of surging were not supported by the statistical analysis. Despite the associations between surging and certain characteristics, no single factor fully explained the observed geographical distribution of surge-type glaciers in Svalbard. Bjuvbreen is a small surge-type in its quiescent phase. Changes in the geometry of the glacier are occurring relatively slowly. This slow rate of change is a function the low accumulation rates on Svalbard glaciers. On the basis of a simple model, the next surge of Bjuvbreen is predicted to occur between .2022- 2055, indicating a comparatively long quiescent period of -90-130 years. Bjuvbreen is comprised of two dynamically distinct zones which are separated by a large bulge. The lower portion of the glacier is inactive and stagnating, in contrast to the active ice up.:.glacier from the bulge. The observed velocity of the active region was compared with various hydrological characteristics of the glacier. The inferred behaviour of water within the glacier seems to have some, although limited, influence on the ice motion. A spatially restricted drainage system is the probable reason for this limited influence of hydrology on glacier velocity.

No description available.

No description available.

A generalized engineering classification method for characterizing Pleistocene glacial materials on the basis of their glaciological mode of origin is presented in this thesis. In formulating the classification an interdisciplinary approach has been adopted. The geotechnical aspects have been based largely on data from extensive site investigations undertaken at the Brenig dam site in North Wales, supplemented where necessary by data obtained from the glaciological and geotechnical literature. Particular attention has been paid to the macrofabric of the deposits in view of the controlling influence that discontinuities exert on engineering behaviour. The glaciological appraisal of the materials has also relied heavily on detailed evaluation of the engineering behaviour and textural properties of the Brenig deposits. However, in order to extend the applicability of the proposed classification to other locations, the site-specific data has been correlated with results from current glaciological research on modern arctic and temperate glaciers. As a prerequisite for such an assessment, a reconstruction of the glacial history of the Brenig site has been attempted. The similar mineralogy of the various glacial deposits and the availability of extensive geotechnical data on the complete suite of materials has made the, site ideal for this purpose. In presenting the results of the studies, the thesis has been divided into four sections. By way of background, in Part I the methodology and scope of the investigations conducted at Brenig are presented. In Part II a comparison is made between the characteristics of Recent glacial deposits and the Pleistocene materials at Brenig. The stratigraphy and glacial chronology of the site are developed in Part III, while in Part IV the geotechnical evaluation of the site is presented and set within the glaciological framework as a basis for the proposed classification.