Rising global air temperatures are causing increased melting across the surfaces of large ice masses such as the Greenland Ice Sheet and the ice caps of Arctic Canada. The fraction of this melt that refreezes within the snow and firn has a large spatial variability across the surfaces of these ice masses. This spatial variability is an important control on the surface mass balance, and has important implications for the interpretation of satellite radar altimetry data sets. The sensitivity of large ice masses to climate change depends on changes in the melt-runoff relationship, and changes in the spatial extents of surface snow zones within the accumulation zone. Therefore, this thesis develops a model used to calculate melt, near-surface refreezing and surface runoff across the surface of a large ice mass. The model is used to predict both stratigraphic changes and bulk snow and firn properties over a melt season across a transect of points. A high-resolution snow and firn data set from Devon Ice Cap is used to calibrate and validate the model. It is then run across a transect covering the entire altitude range of the ice cap for the summers of 2004 and 2006. The model matches measured trends in bulk snowpack variables across the transect in both years. Calculated fraction of melt running off is similar in both years at ~44%, though is sensitive to change in air temperature. Surface mass balance (including internal accumulation), found to be +0.26 Gt in 2004 and +0.18 Gt in 2006, changes in a parabolic way for a linear air temperature change. The model is then applied to the Greenland Ice Sheet without altering any of the calibrated parameters. It is run for two melt seasons, 2004 and 2005, over which model output compares well with measurements of snow depth, sub-surface density and altitudes of snow surface boundaries. The wet snow line responds in a linear way to change in air temperature, and the runoff line is sensitive to the specified depth within the firn of the impermeable layer. Over the next century, the model shows that the dry snow zone will disappear completely under moderate warming scenarios, and the percolation zone will also disappear under intense warming scenarios. Including a more complicated representation of vertical meltwater percolation through the snow and firn grid substantially alters modelled autumn density profiles, and produces more accurate values of meltwater percolation depth and ice fraction within the autumn snowpack. However, bulk snowpack properties are of similar accuracy to the un-modified model. Scaling up of the model, in both spatial and temporal terms, will make it useful for assistance in the interpretation of satellite radar altimetry data sets, as well as assessing future changes in the spatial variability of refreezing and runoff, reducing the uncertainty in long term surface mass balance predictions across large ice masses.

No description available.

No description available.

No description available.

At the beginning of the International Geophysical Year few people were fully aware of the difficulties of conducting an Antarctic ice accumulation program. In fact, the only man of the present generation having made an extensive study of Antarctic firn (metamorphosed snow) was Valter Schytt of the Norwegian-British-Swedish Expedition, 1949-52. Quite probably he was the one man who realized just how bewildering interpretation of stratigraphy of a snow pit wall in Antarctica could be. [...]

An optical microscope coupled to a flow cell was used to investigate ice nucleation on five atmospherically relevant mineral dusts at temperatures ranging from 233 to 247 K. Kaolinite and muscovite particles were found to be efficient ice nuclei in the deposition mode, requiring relative humidities with respect to ice (RHi) below 112% in order to initiate ice crystal formation. Quartz and calcite particles, by contrast, were poor ice nuclei, requiring relative humidities close to water saturation before ice crystals would form. Montmorillonite particles were efficient ice nuclei at temperatures below 241 K, but poor ice nuclei at higher temperatures. In several cases, there was a lack of quantitative agreement between these data and previously published work. This can be explained by several factors including mineral source, particle size, observation time and surface area available for nucleation. Heterogeneous nucleation rates (Jhet) were calculated from the onset data. Jhet values ranged from 60 to 1100 cm-²s-¹ for the five minerals studied. These values were then used to calculate contact angles (θ) for each mineral according to classical nucleation theory. The contact angles measured for kaolinite and muscovite ranged from 6 to 12º; for quartz and calcite the contact angles were much higher, ranging from 25 to 27º. The contact angles measured for montmorillonite were less than 15º at temperatures below 241 K, and above 20º at higher temperatures. The reported Jhet and θ values may allow for a more direct comparison between laboratory studies and can be used when modeling ice cloud formation in the atmosphere. The roles of H₂SO₄ and (NH4)₂SO₄ coatings on the ice nucleating properties of kaolinite were also investigated. Onset data was collected for H₂SO₄ coated and (NH4)₂SO₄ coated kaolinite particles at temperatures ranging from 233 to 247 K. In contrast to uncoated kaolinite particles, which were effective ice nuclei, H₂SO₄ coated particles were found to be poor ice nuclei, requiring relative humidities close to water saturation before nucleating ice at all temperatures studied. (NH4)₂SO₄ coated particles were poor ice nuclei at 245 K, but effective ice nuclei at 236 K.

Submerged sediment-laden ice blocks that form on the intertidal mud flats of the Minas Basin pose a potential threat to tidal turbines planned for deployment in the Minas Passage. Laboratory prepared ice blocks of varying sediment content, salinity, and length scale were melted in seawater of different temperatures. The effect of sediment inclusions on melt rate is related to changes in heat supply and the heat required to melt a unit mass of ice, where the former is affected by the strength of the convective current and the latter by the ice block properties. A melt rate model for submerged sediment-laden ice is developed, with free convection the dominant deterioration mechanism. The model provides probable upper limits to the lifetimes of submerged ice blocks in the field, and has been used to predict lifetimes of large submerged ice blocks using temperatures representative of seawater in the Minas Basin.

No description available.

No description available.

Accumulation of dynamic and thermodynamic forces in the Arctic are decreasing the extent of thin annual sea ice which polar bear rely on for survival. It is imperative that we identify the preferred habitat of polar bears to fully understand their future requirements. In this thesis, surveys of polar bear tracks and the surrounding sea ice variables, at various scales, were recorded. Sea ice roughness was measured through surveys of the sample area in situ, with an electromagnetic induction (EM) system (IcePIC) mounted to a helicopter, and analyzed through advanced synthetic aperture radar (ASAR) images of the study area. In situ Polar bear tracks provided a limited association with the EM sea ice roughness and a negative association to ASAR sea ice roughness. Results indicate a significant association between EM mean values and ASAR brightness means. In addition, EM statistics and ASAR texture statistics were correlated through a best fit regression model. These associations display a remote method to identify preferred polar bear habitat and provide a potential linkage between the regional (EM) and remotely sensed (ASAR) assessment of sea ice roughness.