The cycling of water in the landscape is influenced by climate change on different time scales and in different directions regarding warming or cooling trends. Along with a changing climate, also the landscape and subsurface conditions, such as permafrost extent, may change in a long-term perspective. Permafrost and hydrology are intimately connected but the interactions between them are poorly understood, and the hydrological response to climate change is complex. The first part of this thesis investigates the effects of different drivers of future changes in hydrological flow and water storage components in the present day temperate Forsmark catchment in Sweden. The role of taliks and their influence on the exchange of deep and shallow groundwater in permafrost environments are also studied. This is done by a simulation sequence where the site is exposed to the landscape, climate and permafrost changes expected from site-specific numerical modeling. In the second part of this thesis, present day periglacial hydrological processes are studied in the Two Boat Lake catchment in western Greenland by field and model investigations of the site. The presence of a through talik below the Two Boat Lake, and data from a deep bedrock borehole into the talik, enable studies of the hydrological interactions between the lake and the talik. The spatial and temporal variability of the different water balance components of the catchment are quantified and the interactions between the surface water and the supra- and sub-permafrost groundwater are analyzed. The results show that the investigated changes in climate and permafrost influence hydrology more than the investigated landscape changes. Under permafrost conditions, the general direction of the exchange between deep and shallow groundwater may change relative to unfrozen conditions. The simulation studies of Forsmark show that the relative topography between taliks governs the recharging and discharging conditions, which is consistent with results from Two Boat Lake. The lake is located at high altitude relative to other taliks and hydraulic measurements indicate recharging conditions. The talik recharge is small compared to other water balance components and does not influence the lake level, which instead is found to be controlled by evapotranspiration and water inflow from the active layer. This is concluded from numerical simulations that take into account and combine evapotranspiration with other surface and subsurface hydrological processes. This thesis highlights the need to integrate surface and subsurface process modelling in order to quantitatively understand and represent the dynamics and complexity of hydrological interactions in periglacial catchments.

Ocean circulation in Greenland's large glacial fjords is one mechanism that controls the rate of submarine melting at the termini of Greenland's outlet glaciers. Here we use hourly position data from GPS units deployed on ten large (>100 meter), deep-keeled icebergs in Sermilik Fjord, SE Greenland. We observe and quantify the motions of these icebergs moving through the mélange, fjord, and shelf regimes. In the mélange, icebergs move outward with glacier flow until pushed loose by large calving events. In the fjord, high frequency, low amplitude tidally-driven motions are superimposed on dominant 1-5 day events with net velocities exceeding 0.1 m/s. We interpret these events as two-layer, intermediary circulation driven by winds along the shelf, where icebergs travel southward in the East Greenland Coastal Current. These results showcase the potential of this novel instrumentation to link iceberg motion with circulation in any large glacial fjord.

Icebergs calved from tidewater glaciers represent significant portions of freshwater flux from the Greenland Ice Sheet to the ocean. Using satellite data sets we quantify properties and distributions of icebergs in three fjords with varied properties: Sermilk, Rink Isbræ, and Kangerdlugssûp Sermerssua. Total iceberg volumes in summer in the three fjords average 6.43, 1.69, and 0.19 km^3, respectively, and we calculate cumulative submerged surface areas of iceberg faces to be 213, 55.2, and 7.57 km^2, respectively. We calculate a freshwater flux from iceberg melt of 0.009 – 0.083 m^3 d^-1 in Sermilik Fjord, suggesting a strong potential of iceberg melt water to influence water properties. Properties of icebergs and size distributions are influenced by calving style and grounding line depths of parent glaciers. Variations are represented in the coefficients of generalized Pareto distributions which best describe size distributions in the fjords.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvii, 147 p.: ill. Includes abstract and vita. Advisor: David H. Bromwich, Dept. of Geography. Includes bibliographical references (p. 140-147).

The influence of seasonal influx of supraglacial meltwater on basal water pressures and consequent changes in ice surface velocity has been a focus of research spanning over three decades, particularly focussing on alpine glaciers. Now, with increased recognition for a need to better include glacial hydrology within models of ice dynamics and ice sheet evolution, the ability to predict where and when meltwater is delivered to the subglacial system is paramount, both for understanding the dynamics of alpine glaciers, and of large Arctic ice masses. Studies of the dynamics of outlet glaciers on the Greenland Ice Sheet have received particular attention in recent years, as links between ice acceleration and increased surface melt production are explored. Responses of horizontal and vertical ice velocities to meltwater generated suggest efficient transmission of meltwater from the supraglacial to subglacial hydrological systems. Indeed, in the case of meltwater transfer through the drainage of supraglacial lakes, it has been shown that such build-ups of stored meltwater can force crevasse penetration through many hundreds of metres of ice. This thesis presents a new modelling routine for the prediction of moulin formation and delivery of meltwater to the ice-bed interface. Temporal and spatial patterns of moulin formation through propagation of crevasses and drainage of supraglacial lakes are presented, and quantitative controls on water-driven crevasse propagation are investigated through a series of sensitivity tests. The model is applied to two glacial catchments: the Croker Bay catchment of Devon Ice Cap in High Arctic Canada; and Leverett Glacier catchment of the southwest Greenland Ice Sheet. Through model application to these sites, sensitivities to crevasse surface dimensions, ice tensile strength, ice fracture toughness and enhanced production of surface meltwater are investigated. Model predictions of moulin formation are compared with field observations and remotely sensed data, including ice surface velocities, dynamic flow regimes, and visible surface features. Additionally, model quantification of meltwater delivered to the ice-bed interface of Leverett Glacier is compared with profiles of measured proglacial discharge. Moulin formation is predicted at increasingly high elevation with time into the ablation season in both4catchments, and furthermore, the model predicts an increase in both the number of moulins and the number of lake drainages in response to increased melt scenarios. Sensitivity testing confirms that the model is most sensitive to factors influencing the rate at which meltwater fills a crevasse, and results highlight the importance of accurate parameterisation of crevasse surface dimensions and the tensile strength of the ice. Further applications of the model are discussed, with a focus on incorporation into coupled models of glacial hydrology and dynamics, including larger scale ice sheet modelling. The inclusion of spatially distributed points of temporally varying meltwater delivery to the subglacial system is imperative to fully understand the behaviour of the subglacial drainage system. Furthermore, dynamic response to future climatic change and increased melt scenarios, and the consequent evolution of ice masses, including those in the Canadian Arctic and Greenland, cannot be fully understood without first understanding the glacial hydrological processes driving many of these changes.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 65-69).

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, Sept. 2004. / Thesis advisor(s): Roland W. Garwood. Includes bibliographical references (p. 71-73). Also available online.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xv, 200 p.; also includes graphics. Includes bibliographical references (p. 173-184).

Ice shelves play an important role in the mass balance of an ice sheet, by providing a link between the ocean and ice. Melting at the base of an ice shelf can play a vital role in its mass balance and stability. Topographic channel features have been found on the base of ice shelves, and have been found to alter melting, however the mechanism behind this alteration is unknown. Petermann Glacier is a major outlet glacier in North West Greenland, draining approximately 6% of Greenland Ice Sheet. It terminates in a long, thin ice shelf, constrained within a high-walled fjord. The ice shelf has pronounced longitudinal channel features on its base, which limited observations suggest direct ocean currents in a mixed layer of ocean and melt waters, focusing melt in these regions. Petermann Glacier underwent two large calving events in 2010 and 2012, and the impact of these events, or possible further calving events, on basal melting is unknown. Using the MITgcm to model the ocean cavity beneath an idealised ice shelf, this thesis discusses the impact of basal channels on interactions at the ice base and circulation within the cavity. This is supplemented with a modelling investigation into the interactions beneath Petermann Glacier, and the impact of recent calving events. The inclusion of channels was found to have a stabilising effect on the ice shelf by decreasing the mean basal melt rate, caused by the refocusing, and decrease in intensity of, the meltwater layer flow beneath the ice shelf. This stabilisation and resulting 'survivor bias' explains why channels are commonly found on the base of warm water ice shelves. The model of Petermann Glacier found similar melt patterns to observational studies, however with a lesser magnitude. The calving events of 2010 and 2012 removed areas of ice shelf with low melt rates, resulting in little impact on the overall volume of ice removed through ocean melting, though further calving would vastly reduce the volume of ice melted. One consequence of calving is the increase in melting-induced undercutting at the ice front, leading to the potential for enhanced secondary calving.

During the last twenty years marked declines in Peregrine Falcon populations have occurred in many parts of the world (Hickey, 1969). During recent years the peregrine has been placed on the list of Endangered Species. Several factors have been suggested as the cause of its decline. These include changing climatic conditions (Porter and White, 1973), human disturbance (Mattox, pers. comm.), and introduction of chlorinated hydrocarbons as pesticides into the environment (Ratcliffe, 1970). The third factor, introduction of chlorinated hydrocarbons, has occurred on the American, European and Asian continents. Even peregrines nesting in locations far from human population concentrations are exposed to chemical pollutants on migratory flights south, in nesting areas and in the wintering range. Most of the small birds utilized by the peregrine as prey in the north also migrate south every winter, many moving into farming areas where insecticides are frequently used. By feeding in these areas the passerines accumulate substantial amounts of chlorinated hydrocarbons which are stored in fat tissues. As the peregrines feed on these small birds, body levels of chlorinated hydrocarbons gradually increase. If subsequent levels·are high enough, they may cause death (Porter, 1972). In most cases, however, lethal levels are never reached: instead the lower levels produce eggshell thinning and breakage (Porter and Wiemeyer, 1969) which may be an important reason for world-wide decline in peregrine populations (Hickey and Roelle, 1969). Peregrines in the western United States have shown a 20% decrease in eggshell thickness since DDT was introduced (Enderson and Craig, 1974).