Approved for public release; distribution is unlimited. / The unique properties of the temperature and salinity profiles for polar oceans are critical for high-latitude mixed layer thermodynamics. In the Polar regions the water column is coldest and freshest at the surface where ice may be present. This density structure often leads to entrainment and affects both the mixed layer depth and the ice thickness. Thermobaricity, the combined dependence of seawater thermal expansion on temperature and pressure, magnifies the buoyancy flux associated with mixed layer convection. When thermobaricity amplifies entrainment so that the heat into the mixed layer is greater than the heat leaving the water column, the mixed layer warms and any existing ice begins to melt. Similarly, if the heat entrained is less than the heat leaving the column, the mixed layer cools and freezing occurs at the surface. In the former situation a polynya, or region of no ice surrounded by ice coverage, may form. A one-dimensional vertical model is built, and trial cases are run to show the intricate relationships that govern the heat and salt fluxes and subsequent ice thickness. The model shows the importance of thermobaricity to the air-sea-ice interactions. It also offers significant insight into how relatively constant atmospheric forcing can lead to polynya-like conditions. / Ensign, United States Navy

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Accurately forecasting the contribution of the Greenland Ice Sheet to global sea-level requires precise observations to constrain present-day processes and incorporate them into models. However, the spatial and temporal resolution of satellite imagery and representativeness of in situ measurements often precludes or obscures our understanding of mass loss processes. This thesis investigates whether imagery from unmanned aerial vehicles (UAVs) have the potential to 1) bridge the scale gap between in situ and satellite observations and, 2) resolve processes of mass loss which are beyond the resolution of satellite imagery. It is found that the footprints of ground-based pyranometers are insufficient to capture the spatial heterogeneity of the ice surface as it progressively ablates and darkens. Point-to-pixel albedo comparisons are therefore often invalid, meaning that satellite-derived albedo measurements may be more accurate than previously thought. A 25 km transect intersecting the dark zone reveals that distributed impurities, not cryoconite nor surface water, govern spatial albedo patterns and may have implications for the future expansion of the dark zone. Repeat surveys over Store Glacier show that UAVs can be used to quantify calving rates and surface velocities of tidewater glaciers. The surveys indicate that large calving events cause short-term terminus velocity accelerations and can explain the seasonal pattern of acceleration and retreat. Any process which accelerates calving, such as removal of the ice m ́elange, therefore has important implications for the glaciers future behaviour.

<p>The aim of this study was to examine if it was possible to improve fitness and strength in young ice hockey players with help of a training programme based on functional training and aerobic training. The training programme was performed on Halmstad Hockey U-16 team where 17 boys participated in the study. We performed the training in a period of sex weeks with three training occasions each week. These consisted of two functional training sessions and one fitness session. In the beginning we emphasized the importance of a correct performance and technique. Two test methodes were used to see if the training had given result, Åstrand bicycle ergometer test and Square hop test.</p><p>The result of the training was an increase in leg and trunk strength and fitness on the majority of the participants.</p>

A criterion is defined to compare seasonal ice coverage in the Greenland Sea for the years 1900-57, and the areal coverage is graphed using the 1898-1913 average as a standard. The factors wielding possible influence on short-term variations of the ice cover are examined individually and their relative importance established. The influence of ocean currents is evaluated by analysis of hydrosections across the East Greenland Current at 74°-76° N and across the North Atlantic Current in the Faeroe-Shetland channel. Data from the latter area are used for numerical analysis of heat imported to the Greenland Sea by the North Atlantic Current in the 1927-52 period. Details about the Irminger Current's behavior are derived from station data from Denmark Strait and from surface temperatures at Selvogsbanki south of Iceland. Year-to-year variations are found to exist in the flow volumes of all three currents, and correlations with seasonal ice coverage in the Greenland Sea are shown. Above-average precipitation in conjunction with below-average storm activity is found to have negligible influence on the ice regime, and no significant correlation is found. The possible effect of evaporation is computed to be far below the threshold of detectability. Air temperatures in the Norwegian-Greenland Sea region display a trend of increase throughout the period studied, in harmony with a concurrent trend of decreasing ice cover; but no causal relationship is in evidence. The effects of strengths and directions of predominant winds are examined, and good correlations are shown between ice cover fluctuations and easterly wind components at Norwegian coastal stations. At the points of major currents' entrances to and exits from the Greenland Sea the wind effects are complex and cannot be fully evaluated on the basis of existing data. The fluctuations of ocean currents entering and leaving the Greenland Sea and of water movements within the Greenland Sea remain as the apparent determinant of year-to-year variations of the ice cover. / Graduation date: 1968

Large-extent ice storms have received relatively little attention from researchers. This research investigates the effects of abiotic and biotic factors on the spatial patterns of ice storm disturbance on a forested landscape. This investigation provides a landscape-level perspective on the impacts of ice storm disturbance, clarifies the effects on ecosystem dynamics, and will aid future forest management plans. The study was conducted in Ouachita National Forest (ONF) in west-central Arkansas and southeastern Oklahoma and examined approximately 6000 km2 of forest between 150 and 800 m elevation. Normalized Difference Vegeation Index (NDVI) difference values were calculated using two Landsat 7 ETM+ scenes to identify NDVI changes that potentially were associated with ice storm damage to the forests. Forty-six geolocated field sites were used to determine the relationship of NDVI difference to actual forest damage caused by the ice storm by counting the number of downed tree boles intersecting a 100 m transect. These field sites encompassed a broad range of each of the physical variables (i.e. elevation, slope, and aspect), forest type, and degree of damage. The linear regression model determined the relationship between NDVI difference and ice storm damage. Elevation, slope, and aspect were calculated based on individual pixels from the DEM. Categories of forest damage were based on NDVI difference values. A chi-square test of correspondence and Cramer’s V test were then used to analyze relationships of damage to abiotic and biotic variables. The strong, negative relationship observed in the linear regression model suggested that NDVI was representative of ice storm damage in the study area. The chi-square test of correspondence indicated the abiotic and biotic variables all had associations with NDVI difference results (p<0.001). The Cramer’s V test established that elevation had the strongest influence on the degree of ice storm damage followed closely by slope and aspect. Moderate elevations, moderate slopes, and windward aspects received the highest percentage of major storm damage. Forest type displayed a weak relationship with the extent of damage. The topographic patterns of ice storm damage are similar to patterns found in previous research. Topography influenced spatial patterns of ice storm damage. Elevation, slope, and aspect were all found to be important variables influencing the degree of ice storm damage. Knowledge concerning these spatial patterns is critical for future studies of ecosystem dynamics and forest management practices.

The interannual variability of the sea ice in the Southern Ocean and its evolution projected for the end of the 21st century are investigated using observations and different types of models. First of all, none of the known atmospheric modes of variability are able to explain much of the total sea ice extent variability in the Southern Ocean. However, they have large influences on the local and regional scales. In particular, the response of the sea ice to the Southern Annular Mode is characterized by a dipole between the Ross Sea and the region around the Antarctic Peninsula caused by a low pressure anomaly in the Amundsen Sea in high SAM-index years. Secondly, the sea ice extent in the different regions seems to be mostly uncorrelated, showing that the total sea ice cover cannot be seen as a single entity, but merely as a combination of regional covers. Finally, it is shown why the projected distribution of sea ice is not a simple extrapolation of the current sea ice trends. The mechanisms responsible for the regional variability of the future sea-ice extents are discussed.

The aim of this study was to examine if it was possible to improve fitness and strength in young ice hockey players with help of a training programme based on functional training and aerobic training. The training programme was performed on Halmstad Hockey U-16 team where 17 boys participated in the study. We performed the training in a period of sex weeks with three training occasions each week. These consisted of two functional training sessions and one fitness session. In the beginning we emphasized the importance of a correct performance and technique. Two test methodes were used to see if the training had given result, Åstrand bicycle ergometer test and Square hop test. The result of the training was an increase in leg and trunk strength and fitness on the majority of the participants.

Lakes comprise a large portion of the surface cover in northern North America, forming an important part of the cryosphere. Further alterations to the present day ice regime could result in major ecosystem changes, such as species shifts and the disappearance of perennial ice cover. Lake ice has been shown to both respond to, and play a role in the local/regional climate. The timing of lake ice phenological events (e.g. break-up/freeze-up) is a useful indicator of climate variability and change. Trends in ice phenology have typically been associated with variations in air temperatures while trends found in ice thickness tend to be associated more with changes in snow cover. The inclusion of lakes and lake ice in climate modelling is an area of increased attention in recent studies and the ability to accurately represent ice cover on lakes will be an important step in the improvement of global circulation models, regional climate models and numerical weather forecasting. This thesis aimed to further our understanding of lake ice and climate interactions, with an emphasis on ice cover modelling. The Canadian Lake Ice Model (CLIMo) was used throughout for lake ice simulations. To validate and improve the model results, in situ measurements of the ice cover for two seasons in Churchill, MB were obtained using an upward-looking sonar device Shallow Water Ice Profiler (SWIP) installed on the bottom of the lake. The SWIP identified the ice-on/off dates as well as collected ice thickness measurements. In addition, a digital camera was installed on shore to capture images of the ice cover through the seasons and field measurements were obtained of snow depth on the ice, and both the thickness of snow ice (if present) and total ice cover. Altering the amounts of snow cover on the ice surface to represent potential snow redistribution affected simulated freeze-up dates by a maximum of 22 days and break-up dates by a maximum of 12 days, highlighting the importance of accurately representing the snowpack for lake ice modelling. The late season ice thickness tended to be under estimated by the simulations with break-up occurring too early, however, the evolution of the ice cover was simulated to fall between the range of the full snow and no snow scenario, with the thickness being dependent on the amount of snow cover on the ice surface. CLIMo was then used to simulate lake ice phenology across the North American Arctic from 1961–2100 using two climate scenarios produced by the Canadian Regional Climate Model (CRCM). Results from the 1961–1990 time period were validated using 15 locations across the Canadian Arctic, with both in situ ice cover observations from the Canadian Ice Database as well as additional ice cover simulations using nearby weather station data. Projected changes to the ice cover using the 30-year mean data between 1961–1990 and 2041–2070 suggest a shift in break-up and freeze-up dates for most areas ranging from 10–25 days earlier (break-up) and 0–15 days later (freeze-up). The resulting ice cover durations show mainly a 10–25 day reduction for the shallower lakes (3 and 10 m) and 10–30 day reduction for the deeper lakes (30 m). More extreme reductions of up to 60 days (excluding the loss of perennial ice cover) were shown in the coastal regions compared to the interior continental areas. The mean maximum ice thickness was shown to decrease by 10–60 cm with no snow cover and 5–50 cm with snow cover on the ice. Snow ice was also shown to increase through most of the study area with the exception of the Alaskan coastal areas. While the most suitable way to undertake wide scale lake ice modeling is to force the models with climate model output or reanalysis data, a variety of different lake morphometric conditions could exist within a given grid cell leading to different durations of ice cover within the grid cell. Both the daily IMS product (4 km) and the MODIS snow product (500 m) were assessed for their utility at determining lake ice phenology at the sub-grid cell level throughout the province of Quebec. Both products were useful for detecting ice-off, however, the MODIS product was advantageous for detecting ice-on, mainly due to the finer resolution and resulting spatial detail of the lake ice. The sub-grid cell variability was typically less than 2%, although it ranged as high as 10% for some grid cells. An indication of whether or not the simulated ice-on/off dates were within the sub-grid cell variability was determined and on average across the entire province, were found to be within the variability 62% of the time for ice-off and 80% of the time for ice-on. Forcing the model with the future climate scenarios from CRCM predicts ice cover durations throughout the region will decrease by up to 50 days from the current 1981-2010 means to the 2041-2070 means, and decrease from 15 to nearly 100 days shorter between the contemporary and 2071-2100 means. Overall, this work examined the climate-lake-ice interactions under both contemporary and future climate conditions, as well as provided new insight into sub-grid cell variability of lake ice.

Large-extent ice storms have received relatively little attention from researchers. This research investigates the effects of abiotic and biotic factors on the spatial patterns of ice storm disturbance on a forested landscape. This investigation provides a landscape-level perspective on the impacts of ice storm disturbance, clarifies the effects on ecosystem dynamics, and will aid future forest management plans. The study was conducted in Ouachita National Forest (ONF) in west-central Arkansas and southeastern Oklahoma and examined approximately 6000 km2 of forest between 150 and 800 m elevation. Normalized Difference Vegeation Index (NDVI) difference values were calculated using two Landsat 7 ETM+ scenes to identify NDVI changes that potentially were associated with ice storm damage to the forests. Forty-six geolocated field sites were used to determine the relationship of NDVI difference to actual forest damage caused by the ice storm by counting the number of downed tree boles intersecting a 100 m transect. These field sites encompassed a broad range of each of the physical variables (i.e. elevation, slope, and aspect), forest type, and degree of damage. The linear regression model determined the relationship between NDVI difference and ice storm damage. Elevation, slope, and aspect were calculated based on individual pixels from the DEM. Categories of forest damage were based on NDVI difference values. A chi-square test of correspondence and Cramer’s V test were then used to analyze relationships of damage to abiotic and biotic variables. The strong, negative relationship observed in the linear regression model suggested that NDVI was representative of ice storm damage in the study area. The chi-square test of correspondence indicated the abiotic and biotic variables all had associations with NDVI difference results (p<0.001). The Cramer’s V test established that elevation had the strongest influence on the degree of ice storm damage followed closely by slope and aspect. Moderate elevations, moderate slopes, and windward aspects received the highest percentage of major storm damage. Forest type displayed a weak relationship with the extent of damage. The topographic patterns of ice storm damage are similar to patterns found in previous research. Topography influenced spatial patterns of ice storm damage. Elevation, slope, and aspect were all found to be important variables influencing the degree of ice storm damage. Knowledge concerning these spatial patterns is critical for future studies of ecosystem dynamics and forest management practices.