Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 177-204). Also available via the World Wide Web.

Understanding how debris-covered glaciers respond to climate is necessary in order to evaluate future water resources and glacier flood hazard potential, and to make sense of the glacier chronology in mountain regions, In order achieve this, it is necessary to improve the current understanding of how surface debris affects glacier ablation rate, and to develop methods by which the ablation of debris-covered glaciers can be predicted under various climatic scenarios. This thesis develops a numerical surface energy balance model that uses simple meteorological data to calculate melt beneath a debris layer of given thickness and thermal characteristics. Field data from three contrasting sites demonstrate that the assumptions made within the model concerning the thermal properties of supraglacial debris are valid during most ablation conditions and that model performance is considerably better than previous models. Model results indicate that the effect of debris on melt rate is highly dependent on meteorological conditions. Under colder climates, thin debris can accelerate ice melt by extending the ablation period at both diurnal and seasonal scales. However, in milder mid- summer conditions, even a very thin debris cover inhibits melt rate compared to that of exposed ice. The new melt model is applied to produce the first quantified ablation gradients for debris- covered glaciers, and to model the evolution of ice surfaces under a debris layer of variable thickness. Modelled ablation gradients are qualitatively similar to hypothetical ones outlined previously, and quantitatively similar to those measured in the field. The ablation gradients are used to explore the factors affecting the response of debris-covered glaciers to climate change. Beneath a debris layer of variable thickness, the melt model produced ablation topography, as observed in the field, which underwent topographic inversion over time in response to debris redistribution. Debris thickness variability was found to cause calculated ablation rate to increase compared to that calculated using a mean debris thickness by one to two orders of magnitude, suggesting that melt calculations made on the basis of spatially averaged debris thickness may be inaccurate.

A mass balance approach was used in an attempt to quantify nutrient flux to the nearshore at the West Coast, Barbados, W.I. Total nitrogen and total phosphorus levels of the groundwater at inland pumping stations and above beach margins, as well as in the water of the nearshore zone and approximately 2 km offshore, were obtained. Nearshore groundwater seepage rates and salinity data were also taken. This study attempted to use this raw data to estimate flushing rates, nutrient loading rates, and nutrient loss rates, to ultimately create a picture of the fate of nutrients as they travel in groundwater into the nearshore zone. Annual loading for the entire West Coast was calculated at 1.46 x 105 kg NO3---N for nitrogen and 1.19 x 103 kg PO4 3---P for phosphorus. Mean nutrient levels in groundwater above the beach margin were estimated at 969.83 muM for nitrogen and 3.63 muM for phosphorus. For nitrogen and phosphorus respectively, these levels were twice and three times higher than at the pumping stations farther inland; and there was also a fourfold and fivefold drop in nitrogen and phosphorus, respectively, in the nearshore zone relative to this groundwater above the beach margin. This indicated that the dense coastal population at the West Coast was adding significant amounts of nutrient to groundwater after it had left the inland pumping stations. There were no patterns of gradation in nutrient concentrations detected within the immediate nearshore, making completion of an accurate mass balance impossible, though indicating that there was significant advection of submarine groundwater offshore, beyond the study zone. This may contribute to the poor health of West Coast reefs, where sewage and fertiliser leaching and runoff are suspected as the primary sources for nutrient input to submarine groundwater to the south and northern parts of the West Coast, respectively.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (p. 70-75). Also available via the World Wide Web.

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