This dissertation attempts to improve the understanding of spatial distribution and evolution of snow-covered sea ice as related to polar bear habitat. This will be accomplished at both the local (i.e. 1m spatial resolution) and regional scales (i.e. 100 km spatial resolution) for various types of first-year sea ice (FYI) through four primary objectives. The first primary objective (i.e. Chapter 3) examines the observed and modeled temporal evolution of snow over smooth FYI, as well as the estimation of on-ice meteorological conditions. Results suggest that increases in observed snowdrifts and changes to the orientation of the drifts are related to snowfall and drifting events. Modeling these changes over time using a spatially distributed snow model is not able to accurately estimate the snow distribution. As well, only the on-ice temperature and humidity can be estimated from land-based station data, limiting the modeling of snow over sea ice. The second primary objective (i.e. Chapter 4) extends this research to rough FYI types, more relevant to polar bear habitat. More specifically this objective studies the spatial pattern of snow distribution over rough ice and ridges and the relationship between ice roughness and meteorological conditions. Results suggest that ice roughness influences the magnitude of snow depth, while the wind direction during periods of snow deposition and/or blowing snow events will impact the spatial pattern. The third primary objective (i.e. Chapter 5) focuses on developing a more feasible method of deriving surface roughness. This objective attempts to use satellite imagery and texture analysis to derive surface roughness for snow-covered sea ice. Results suggest that a Gamma speckle reduction filter, coupled with a grey-level co-occurrence matrix texture measure (Entropy or Angular Second Moment) is able to account for more than 88% of the variability in the surface roughness. The final primary objective (i.e. Chapter 6) examines the temporal evolution and factors controlling the changes in sea ice characteristics over regional scale for a period from 1978 to 2002. Observed anomalies in sea ice characteristics within some of the polar bear subpopulations may be explained by thermodynamic and/or dynamic factors. Results suggest that published reduction in polar bear population and condition within the subpopulations co-occur with these observed changes in sea ice characteristics.

Recent research indicates climate change will be amplified in Polar Regions, which will cause decreases to sea ice thickness and extent throughout the Arctic. Polar bears (Ursus maritimus) will be directly affected by changes to Arctic sea ice conditions because they rely on the ice substrate for numerous aspects of their life history. Perhaps of most importance, polar bears use the sea ice platform to access their main prey, pagophilic seals. Determining specific effects of climate-induced environmental change on polar bears will require monitoring at numerous spatiotemporal scales and across various levels of biological organization. In this dissertation I used and refined a variety of ecological monitoring tools that evaluated the effects of seasonal and longer-term unidirectional sea ice changes to various aspects of polar bear ecology. At a molecular level, I used urea to creatinine ratios in polar bear blood to show that an increased number of polar bears were in a physiological fasting state during spring captures in 2005-2006 compared to the mid-1980s. These changes corresponded to broad-scale changes in Arctic sea ice composition, which may have altered prey availability. I also used measurements of naturally occurring stable isotopes (δ13C, δ15N) in polar bear tissues to examine their diet, which included both lipid-rich blubber and the proteinaceous tissues of their marine mammal prey. Because the proportion of proteins and lipids consumed likely depended on prey type and size, it was necessary to consider metabolic routing of these macromolecules separately when using isotope mixing models to determine and monitor polar bear diet. I also monitored polar bear movement and migration behaviour at the population level. Specific landscape sea ice metrics corresponded to seasonal population migration patterns and fidelity to particular geographic regions. Trends in the timing of these seasonal population migration patterns were likely associated with climate-induced changes to sea ice dynamics. Finally, I examined migration behaviour in relation to local sea ice dynamics in individual polar bears and demonstrated a mechanistic understanding of the relationship between sea ice and polar bear migration patterns. / Ecology

The world is dominated by cold environments that include the poles, the deep ocean, and alpine regions. Polar algae support the aquatic food chain and are increasingly threatened by climate change. With a changing climate, ice cover is decreasing with increased temperatures, leading to changes in light availability and salinity. Using two closely related but geographically distant algal species, Chlamydomonas priscuii and Chlamydomonas malina, we examined how the heat stress responses changed depending on their culturing conditions. C. malina was isolated from the Beauford Sea in the Canadian Arctic and C. priscuii is from the permanently ice-covered Lake Bonney, Antarctica. This work looks at two questions; (1) how cold adapted algae responds to changing conditions and subsequent heat stress, and (2) what contributes to stress resistance? We found that algae show robust growth across a wide spectrum of light and salinity but have the fastest growth rates at low salinity and high light intensities. These fast-growing algae are the most susceptible to heat stress indicating liability during climate change. High salinity grown algae were more resilient when challenged by heat stress in the terms of maintaining photosynthetic efficiency, attenuated ROS production, and delayed cell death. At high salinity C. priscuii produces high levels of glycerol which for the first time in green algae has been shown to contribute to thermotolerance. Overall, this work provides insight into the stress resilience of psychrophiles, something that is especially pertinent in our age of rapid climate change.

The most compelling evidence of the complex interaction between the geomagnetic field of the Earth and the magnetic field of the Sun is found in the polar ionosphere. Large scale F-region plasma density perturbations result from the coupling between the two fields. Plasma density enhancements known as ionization patches, and depletions can have lifetimes of several hours in the F region and are almost always present everywhere throughout the nighttime polar ionosphere. The perturbations can seed ionospheric irregularities that severely hamper communication and navigational networks, even during times of subdued geomagnetic activity. Up until recently, it has been difficult to study the perturbations due to the remoteness of their location. In the past decade an array of optical and radio instruments have been deployed to the Canadian sector of the Arctic, enabling a more thorough sampling of the polar ionosphere and the large scale perturbations therein. In this work, common volume measurements from the Rankin Inlet Super Dual Auroral Radar Network (SuperDARN), Resolute Bay Incoherent Scatter Radar - North (RISR-N) and Optical Mesosphere and Thermosphere Imagers (OMTI) system at Resolute Bay are employed to investigate the generation mechanisms, transport properties, and optical and radio signatures of the large scale perturbations. A model connecting the optical signatures of patches to their velocity profile through the ionosphere is introduced and applied to OMTI data. In addition, an algorithm is developed to detect the presence of patches using RISR-N. Using the algorithm, a survey of patches sampled over several days is conducted, providing a comprehensive account of the variable polar ionosphere in terms of its plasma state parameters. Furthermore, the algorithm is used to diagnose patches as a primary source of coherent backscatter for the Rankin Inlet SuperDARN radar. Lastly, the generation of a deep plasma density depletion is analyzed using the three aforementioned instruments. Using a model, it is shown that such perturbations can be forged by intense frictional heating events in the polar ionosphere on a time scale of 15 minutes, and can subsequently be transported through the region.

Measurements by the TOMS instrument aboard the Nimbus 7 satellite, of total column ozone over polar regions have been studied to determine the effects of solar induced natural ozone modulation. Two different analysis methods were employed to ascertain short term (days to months) and long term (months to years) solar influences on polar ozone. Bursts of intense solar activity can result in solar proton events (SPE's). The high energy protons, originating in solar flares, produce secondary electrons which can generate large concentrations of odd nitrogen in the middle atmosphere. These reactive species can catalytically destroy ozone. Three case studies are presented in an attempt to quantify the effect of SPE's on ozone mass over a latitude region 90 to 70°. In order to monitor the ozone response following a SPE over both hemispheres simultaneously, the SPE must occur during the equinox period when both poles are irradiated. Fortuitously, a SPE was recorded in March 1989, the analysis of which forms a case study in this thesis. Ozone depletions of 7.4 x 10 to the power of 9 kg for the south polar cap and 8.0 x 10 to the power of 9 kg for the north polar cap indicate the degree of symmetry for this event. Longer term effects of solar variability are investigated by Fourier techniques. A Fourier transform of eleven years of total ozone mass values, over the region 90 to 70° S, was performed. Inspection of the Fourier spectrum reveals peaks associated with solar cycle, annual and semi-annual oscillations, that may be attributed directly to solar variation. Other peaks, corresponding to QBO and ENSO periodicities, may be ascribed to indirect solar influences i.e. thermally driven dynamics. Finally, a comparison between the phase of the solar cycle peak in this spectrum with that in a spectrum of daily values of solar radio flux, reveals that the austral polar ozone solar cycle periodicity lags solar forcing by 2.8 years. Portions of chapters have been reported at the 1990 South African Institute of Physics Annual Conference, University of Port Elizabeth, South Africa and as a poster at the 1992 Quadrennial Ozone Symposium, Charlottesville, United States of America, 4-13 June 1992. In addition, various parts of this work has been submitted for publication, viz: Stephenson, J. A. E. and M. W. J. Scourfield, Importance of energetic solar protons in ozone depletion, Nature, 352, 137: 1991. / Thesis (Ph.D.)-University of Natal, Durban, 1994.

All of the members of the microsporidia possess a unique, highly specialized invasion mechanism that involves the polar tube and spore wall. This chapter reviews the data on the organization, structure, and function of this invasion organelle. The application of immunological and molecular techniques and recent genome sequencing data has resulted in the identification of multiple polar tube and spore wall proteins (SWPs). The interactions of these identified proteins in the formation and function of the polar tube and spore wall remain to be determined. Inside the spore, the polar tube is filled with material and is often termed the polar filament; however, this chapter uses the term polar tube to refer to this structure when it is within the spore as well as when it forms a hollow tube after germination and is found outside the spore. The chapter presents details on the spore activation and discharge.

The primary objective of the NASA sponsored ICESat mission is to study the short and long term changes in the ice mass in the Greenland and Antarctica regions. The satellite was therefore placed into a frozen near-polar near-circular repeat groundtrack to ensure an adequate coverage of the polar regions while keeping the groundtrack periodic and reducing the variations in the orbital elements, and more specifically the semi-major axis of the ICESat orbit. After launch, a contingency plan had to be devised to compensate for a laser that dangerously compromised the lifetime of the ICESat mission. This new plan makes an intensive use of the ICESat subcycles, a characteristic of the repeat groundtrack orbits often over-looked. The subcycle of a repeat groundtrack orbit provide global coverage within a time shorter than the groundtrack repetition period. For a satellite with an off-nadir pointing capacity, the subcycles provide near-repeat tracks which represents added opportunity for altimetry measurement over a specific track. The ICESat subcycles were also used in a very innovative fashion to reposition the satellite within its repeat cycle via orbital maneuvers called phasing maneuver. The necessary theoretical framework is provided for the subcycle analysis and the implementation of phasing maneuvers for any future repeat orbit mission. In the perspective of performing cross-validation of missions like CryoSat using the ICESat off-nadir capacity, a study was conducted to determine the geolocations of crossovers between two different repeat groundtrack Keplerian orbits. The general analytical solution was applied to ICESat vs. several other repeat groundtrack orbit mission, including the future ICESat-II mission. ICESat’s repeat groundtrack orbit was designed using a disturbing force model that includes only the Earth geopotential. Though the third body effect from the Sun and the Moon was neglected in the orbit design, it does in fact disrupt the repeatability condition of the groundtrack and consequently implies orbit correction maneuvers. The perturbations on ICESat orbit due to the third body effect are studied as a preliminary work towards including these forces in the design of the future ICESat-II repeat groundtrack orbit. / text

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