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.

Seasonal ice cover off Canada's east coast was examined in relation to synoptic scale atmospheric events. Ice concentration information derived from Nimbus-7 scanning multichannel microwave radiometer (SMMR) measurements of surface brightness temperatures, supplemented by AES composite ice charts, provided timely coverage of the study area during the 1971/72, 1980/81 and 1984/85 ice seasons, 1971/72 and 1984/85 seasons with high ice concentrations and 1980/81 a season with low concentrations. / Atmospheric variability was monitored using the 850 hPa height at three upper air stations along the western edge of the study region. Additional information was drawn from storm track records, providing an indication of surface variability. Properties of specific storm events were obtained from the storm track data, permitting evaluation of the ice response to passing synoptic disturbances. / Results of this investigation indicate that, (1) passive microwave-derived ice information can be used to monitor high frequency variability in the marginal ice, (2) despite short time series, spectral relationships between ice concentration variability and 850 hPa pressure height indicate a strong association between the two at synoptic frequencies zone, and (3) variability in ice cover extent and concentration can be related to the passage of individual synoptic events.

Motivated by studies of non-magnetic dopings of pyrochlore spin ice and the experimental realization of the hyperkagome lattice in Na4Ir3O8, this work studies the dipolar ice model on the hyperkagome lattice. This is a local <111> Ising model with classical spins featuring an antiferromagnetic neighbour exchange as well as a long range dipolar interaction, previously studied on the pyrochlore lattice. A hybrid single spin flip/loop algorithm Monte Carlo code has been developed to address ergodicity issues seen at low temperatures. This algorithm agrees with analytical results for the smallest system size and has been extended to larger system sizes. A phase diagram very similar to that of the pyrochlore lattice is found with an antiferromagnetic region as well as regions with a spin ice crossover and a low temperature ordering transition. An additional charge-ordered state, similar to that in the recently studied kagome spin ice, was also found.

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Bakgrund: Ishockey är en sport som i studier visat sig ha en hög skadefrekvens. Sporten utövas av kvinnor likväl som män men hur sporten spelas skiljer sig åt beroende av kön samt mellan olika länder. En kartläggning av skadeproblematiken utgör första steget i ett skadepreventivt arbete. Dock finns i dagsläget inga studier angående skadepanoramat inom svensk damishockey. Syfte: Att kartlägga skadeproblematiken inom svensk damishockey utifrån ålder, antal exponeringstimmar, skadelokalisation, skadetillfälle, skadefrekvens samt hur lång matchfrånvaro skador föranleder. Att undersöka samband mellan skadefrekvens och exponeringstimmar samt skadefrekvens och ålder. Metod: En webbaserad enkät utformades i en retrospektiv design. Populationen var samtliga spelare aktiva i riksserien och division 1 i Sverige under säsongen 2013-2014. Data insamlades fortlöpande under tre veckor i februari 2014. Resultatsammanfattning: Antal kompletta enkätsvar som inkluderades var 137, ca 25 % av populationen. Den vanligaste skadelokalisationen var knät (20 %, n = 25). Knäskador var även kopplade till näst längst matchfrånvaro (medelvärde: 6,5 veckor). Mellan träning och match var skadefördelningen jämn. Flest matchskador inträffade i period 2 (45 %). En signifikant korrelation kunde ses gällande ökat antal skador vid ökat antal exponeringstimmar. Ingen korrelation mellan ålder och skadefrekvens noterades.  Konklusion: Denna studie visar, liksom studier på herrishockey och damishockey i Nordamerika, att knäskador är vanligt förekommande samt att flest matchskador sker i period två. I motsats till föregående studier visar denna ingen signifikant skillnad i skador sett till ökad ålder. Även huvudskadorna visade kraftigt lägre siffror än vad tidigare presenterats inom ishockey. Vidare studier behövs för att kunna utarbeta skadeförebyggande åtgärder framförallt för knäskador / Background: Ice hockey is a sport with high risk for injuries. The practitioners of the sport are both males and females, yet how the game is played differs due to gender and country. Mapping out injuries within the population makes a first step towards injury prevention. However, there are no studies regarding the prospect of injuries in Swedish female ice hockey.  Purpose: Mapping out age, exposure to the sport, location, occasion and time loss related to injuries. Study correlation between player age and number of injuries; exposure hours and number of injuries. Procedure: A web-based questionnaire was made in a retrospective design. The population were all players in riksserien and division 1 in Sweden during the season 2013-2014. Data were collected continuously during three weeks in February 2014. Results: The number of complete questionnaires included was 137, approximately 25 % of the population. The most common injury localisation was the knee (20 %, n = 25). Knee injuries also had the second longest absence from gameplay (mean: 6,5 weeks). The distribution of injuries between training and gameplay were equal. The highest number of injuries during gameplay occurred in the second period (45 %). A significant correlation indicated that more injuries occurred with more exposure hours. No correlation between age and injury were found.  Conclusions: This study shows, as studies on men’s ice hockey and female ice hockey in North America that knee injuries are common and that most of injuries during gameplay occurs in the second period. In opposite to previous studies this study shows no correlation between injuries and age. The head-injuries also showed lower numbers than previous studies. Further studies need to be done to work out interventions for injury prevention, especially for knee injuries.

The purpose of this study is to develop, evaluate, and apply a CRISSP-2D river ice model for a highly complex reach of the Nelson River upstream of the Jenpeg Generating Station in northern Manitoba. The calibrated model is applied in a backcasting scenario to evaluate its potential of predicting the river ice regime associated with specific hydraulic and meteorologic conditions. Secondly, a real-time application is conducted in collaboration with Manitoba Hydro to forecast overnight ice conditions as part of the 2011 Ice Stabilization Program. The model is shown to be fully capable of predicting the onset and type of ice regime that occurs. Spatial variation in ice generation across the study region is accurately captured, including locations of thermal bridging and initial ice front advance. Several modelling limitations associated with parameterization limit model accuracy during the latter stages of freeze-up and are identified as enhancement opportunities.

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.

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.

Previous understanding of the winter ice regime in Hudson Bay was limited. This investigation demonstrates the existence of a large coastal polynya in northwestern Hudson Bay. Measuring approximately 600 km long by 60 km wide, this polynya is typically opened and maintained by surface winds for periods of one to five days. Closing mechanisms result from decline in wind maintenance and apparent thermodynamic ice formation. Open water is present on the northwest coast at some size for up to 70% of the winter between ice formation and breakup. Observation of this open water during the period of the winter ice pack indicates that the ‘ice factory’, modelled previously, in northwest Hudson Bay exists. This furthers understanding of the freshwater budgets, stratification, and atmosphere-ocean interactions while presenting new questions about climate change and the future of the Hudson Bay physical system.

The low temperature spin dynamics of the canonical dipolar spin ice materials is examined. The ac susceptibility of dipolar spin ice materials Ho2Ti2O7 and Dy2Ti2O7 is measured to lower temperatures and frequencies than previous studies. This provides a probe of the dynamics of fractionalized magnetic excitations which have been found to exist and interact as monopole-like particles within the spin ice con guration. Low temperatures and low frequencies access the dilute monopole phase, and provide a valuable stress case scenario to theory which has been used to describe the system to date. The relaxation is found to be well described at the lowest temperatures by an Arrhenius law with single energy barrier for both Ho2Ti2O7 and Dy2Ti2O7, with similar barriers to relaxation, 10.7 K and 9.79 K respectively. It is also revealed to be distinctly different from predictions of the dipolar spin ice model, based upon simulations of both a Coulomb gas and dipolar spin ice on the pyrochlore lattice. These simulations, as well as calculations based on Debye-Huckel theory, do not see Arrhenius behaviour in our temperature range, and do not predict the rate at which dynamics freeze out. It is not currently understood what would be required in order to amend this. The implications for thermal methods of probing spin dynamics is discussed, as well as how this measurement impacts the magnetolyte theory of spin ice. Brief reports are presented in the appendices of specific heat measurements of three spin liquid candidates: Yb2Ti2O7, Tb2Ti2O7, and Pr2Hf2O7. In Yb2Ti2O7, measurements of three single crystals, two unique features, a broad anomaly at 195 mK and sharp peak at 265 mK, are found which seem to comprise elements of previous single crystal and polycrystalline measurements. These low temperature features do not correspond to changes in neutron scattering intensity at 400 mK. In Tb2Ti2O7, a second order transition is found, corresponding to the emergence of a mode in inelastic neutron scattering. Absence of an ordering transition in the suspected <111> antiferromagnet Pr2Hf2O7 is also shown, with specific heat measured down to 100 mK with no ordering transition.