The declining summer Arctic sea ice is impacting cyclone-forcing of dynamic and thermodynamic processes in Arctic sea at different spatial and temporal scales throughout the annual cycle. A catalogue of daily synoptic weather types is generated for the southern Beaufort Sea, covering the period 1979 to 2011 using NCEP/NCAR reanalysis mean sea level pressure data, principle components and k-means cluster analyses. Synoptic type statistics are used to assess changes in atmospheric circulation characteristics, sea ice vorticity, and lead formation. Significant (p < 0.05) seasonal synoptic type frequency anomalies are revealed between 1979 – 1998 and 1999 – 2011, and indicate a stronger Beaufort high, and increased easterly wind forcing in autumn and winter. High rates of young ice production in November and December 2007 were linked to strong easterly wind forcing. A case study of the atmospheric boundary layer during a lead formation event (03 – 18 February 2008) revealed sensible heat fluxes between 0 – 80.14 W • m2 (13 February 2008). First-ever observations of a physical forcing mechanism between Arctic cyclones, the Arctic Ocean, and Arctic sea ice within the southern Beaufort Sea were observed on 06 September 2009. Large swells intruded into the multi-year pack ice, causing instantaneous widespread fracturing, and reduced the large (>1 km) parent ice floes to small (100 – 150 m diameter) floes. This process increased the ice floe perimeter exposed to the ocean by a factor of 4.5. Analysis of Radarsat-2 imagery showed that open water fractional area in the multi-year ice cover initially decreased from 3.7% to 2.7%, then increased to ~20% due to wind-forced divergence. 11.54 MJ • m-2 of additional energy was estimated for lateral melting as a result of the fracture event using radiation budgets prior to and following the event. Earlier occurrences of flexural fracture could hypothetically provide up to three times more additional energy for lateral melt. Furthermore, this process may increase the likelihood of storm-driven upwelling of ocean heat, thereby enhancing bottom melt in the ice cover. This process is therefore presented as a potentially powerful positive feedback process that may accelerate the loss of Arctic sea ice.

The estimation or modeling of biophysical variables such as surface roughness, vegetation phytomass, and soil moisture in the Arctic is an important step towards understanding arctic energy fluxes, effects of changing climate, and hydrological patterns. This research uses Synthetic Aperture Radar (SAR) data, along with ancillary optical and environmental data, to create models that estimate these biophysical variables across different High Arctic landscapes, with the goal of applying the models across even larger areas. Field work was conducted at two High Arctic locations on Melville Island, Nunavut, Canada. At each location, surface roughness values were measured at a number of randomized plot locations using a pin meter. Soil moisture values were measured using a time domain reflectometry (TDR) instrument within six hours of multiple overpasses of the RADARSAT-2 SAR sensor. Surface roughness models were generated with multi-incidence angle and fully polarimetric SAR data, with resulting R2 values ranging between 0.39 and 0.66, and normalized root mean squared error (N_RMSE) values of 14% - 22%. The output from the final surface roughness model was used as an input to the soil moisture models. Vegetation phytomass was modeled with multi-angular SAR data, using a soil adjusted vegetation index (SAVI) derived from optical data across the study area as a measure of verification. The resulting model had a significant (p <0.05) relationship to the SAVI values, with an R2 of 0.60. This model was then compared to field-collected above-ground phytomass values, and a model was derived that related SAR data directly to phytomass. This model again showed a strong relationship, with an R2 value of 0.87. The final biophysical variable that was modeled, soil moisture, showed moderate agreement to field-measured soil moisture values (R2 = 0.46, N_RMSE = 0.15%), but much stronger relationships were found for relative moisture values at fine scales across the landscape. These models, when taken together, demonstrate that SAR data is capable of modeling biophysical variables across high latitude environments. These models will help address larger questions, such as how SAR can be used to better understand moisture and energy exchanges over regional areas in high arctic environments. / Thesis (Ph.D, Geography) -- Queen's University, 2014-02-03 16:52:26.856

The importance of the cryosphere, and of sea ice in particular, for contaminant transport and redistribution in the Arctic was pointed out in the literature. However, studies on contaminants in sea ice are scarce, and entirely neglect the sea ice geophysical and thermodynamic characteristics as well as interactions between various cryospheric compartments. This thesis addresses those gaps. Ice formation was shown to have a significant concentrating impact on the levels of HCHs in the water just beneath the ice. Both geophysical and thermodynamic conditions in sea ice were shown to be crucial in understanding pathways of accumulation or rejection of HCHs. Although HCH burden in the majority of the ice column remains locked throughout most of the season until the early spring, upward migration of brine from the ice to the snow in the winter has an effect on levels of HCHs in the snow by up to 50 %. In the spring, when snow melt water percolates into the ice delivering HCHs to the upper ocean via desalination by flushing, levels of HCHs in the ice can increase by up to 2 %-18 % and 4 %-32 % for α- and γ-HCH, respectively. Brine contained within sea ice currently exhibits the highest HCH concentrations in any abiotic Arctic environment, exceeding under-ice water concentrations by a factor of 3 in the spring. This circumstance suggests that the brine ecosystem has been, and continues to be, the most exposed to HCHs. α-HCH levels were shown to decrease rapidly in the last two decades in the Polar Mixed Layer (PML) and the Pacific Mode Layer (PL) of the Beaufort Sea due to degradation. If the rate of degradation does not change in the near future, the majority of α-HCH could be eliminated from the Beaufort Sea by 2020, with concentrations in 2040 dropping to < 0.006 ng/L and < 0.004 ng/L in the PML and the PL, respectively. Elimination of α-HCH from sea water takes significantly longer than from the atmosphere, with a lag of approximately two decades.

Improved characterization of cloud and precipitation features are required to understand the impact of a changing climate in high latitude regions and accurately represent these features in models. The importance of cold season precipitation to regional moisture cycling and our limited understanding of orographic cloud and precipitation processes in the Arctic provide the motivation for this research. Using high-resolution datasets collected during the Storm Studies in the Arctic (STAR) field project this thesis examines cloud and precipitation features over southern Baffin Island in Nunavut. Cloud and precipitation features were shown to differ over orography compared to the adjacent ocean regions upstream. Gravity waves, terrain shape, atmospheric stability and atmosphere-ocean exchanges were all associated with precipitation enhancement. In addition, high sea ice extent, low-level blocking in the upstream environment and sublimation were factors that reduced precipitation. The nature of hydrometeors was variable and accretion and aggregation were found to be important determinants of whether precipitation reached the ground. The processes controlling a snowfall event over southern Baffin Island were found to be complex, representing a significant challenge for modelling in the region. Low-level convection over adjacent ocean regions, strong upslope flow over the terrain, and the passing of a weak trough collectively produced the event. Analysis of the Global Environmental Multi-scale limited area model (GEM-LAM 2.5) revealed that upstream convection and upslope processes were affected by model errors. Consequently, precipitation onset was delayed and total modelled accumulation was 50% less than observations. Further evaluation of a numerical weather prediction model during STAR cases provided descriptions of model errors and proficiencies for different synoptic forcing and surface environments. Overall the model overestimated temperature and had difficulties representing thermal inversions over sea ice. The model generally over-predicted moisture with the exception of profiles over sea ice and land. Wind speed was frequently underestimated, weakening upslope processes and errors in wind direction were large at times. Cloud-tops were usually too high and cloud-bases too low. Where multiple cloud layers were present, the dry layer depth was inaccurate. Model errors were shown to have implications for cloud and precipitation production and their forecast.

The declining summer Arctic sea ice is impacting cyclone-forcing of dynamic and thermodynamic processes in Arctic sea at different spatial and temporal scales throughout the annual cycle. A catalogue of daily synoptic weather types is generated for the southern Beaufort Sea, covering the period 1979 to 2011 using NCEP/NCAR reanalysis mean sea level pressure data, principle components and k-means cluster analyses. Synoptic type statistics are used to assess changes in atmospheric circulation characteristics, sea ice vorticity, and lead formation. Significant (p < 0.05) seasonal synoptic type frequency anomalies are revealed between 1979 – 1998 and 1999 – 2011, and indicate a stronger Beaufort high, and increased easterly wind forcing in autumn and winter. High rates of young ice production in November and December 2007 were linked to strong easterly wind forcing. A case study of the atmospheric boundary layer during a lead formation event (03 – 18 February 2008) revealed sensible heat fluxes between 0 – 80.14 W • m2 (13 February 2008). First-ever observations of a physical forcing mechanism between Arctic cyclones, the Arctic Ocean, and Arctic sea ice within the southern Beaufort Sea were observed on 06 September 2009. Large swells intruded into the multi-year pack ice, causing instantaneous widespread fracturing, and reduced the large (>1 km) parent ice floes to small (100 – 150 m diameter) floes. This process increased the ice floe perimeter exposed to the ocean by a factor of 4.5. Analysis of Radarsat-2 imagery showed that open water fractional area in the multi-year ice cover initially decreased from 3.7% to 2.7%, then increased to ~20% due to wind-forced divergence. 11.54 MJ • m-2 of additional energy was estimated for lateral melting as a result of the fracture event using radiation budgets prior to and following the event. Earlier occurrences of flexural fracture could hypothetically provide up to three times more additional energy for lateral melt. Furthermore, this process may increase the likelihood of storm-driven upwelling of ocean heat, thereby enhancing bottom melt in the ice cover. This process is therefore presented as a potentially powerful positive feedback process that may accelerate the loss of Arctic sea ice.

Arctic surface air temperatures have been warming at twice the global rate, making it one of the most susceptible regions to current climate change. Effects on cold-adapted aquatic species, such as the culturally and ecologically important Arctic charr (Salvelinus alpinus), are difficult to anticipate and may vary depending on site-specific attributes. Temperature has a direct influence on aspects of species’ fitness, including growth, reproduction and, ultimately, survival. Previous research on temperature-growth patterns in Arctic charr has yielded variable results, particularly for studies observing these patterns in the wild. Two field-based studies are presented in this thesis, in an attempt to better understand temperature-growth patterns for wild populations of Arctic charr. In the first study, individual measurements of annual, or within-season growth were determined from tag-recaptured Arctic charr and examined in relation to summer sea surface temperatures and within-season capture timing in the Ungava and Labrador regions of eastern Canada. Differences in among-year growth were significant for Ungava Bay Arctic charr, with growth being positively correlated with temperature. Growth of Labrador Arctic charr did not vary significantly among years. Regional comparisons demonstrated that Ungava Arctic charr had significantly higher annual growth rates, with differences among years in all regions being positively correlated with temperature. Within-season growth rates of Labrador Arctic charr peaked in June, declined toward August, and were negatively correlated with the length of time spent at sea and mean experienced sea surface temperatures. A quadratic model relating growth rate to temperature best explained the pattern of within-season growth. The higher annual growth of Ungava Bay Arctic charr was attributed to the high sea surface temperatures experienced in 2010-11 and the localized differences in nearshore productivity as compared to Labrador. Results suggest that increases in water temperature may have profound consequences for Arctic charr growth in the Canadian sub-Arctic, depending on the responses of local marine productivity to those same temperature increases. In the second study, oxygen stable isotope temperature reconstruction methods were used to estimate mean experienced summer temperatures from growth zones within individual otoliths of Arctic charr sampled from contrasting lake environments. For either lake, otolith-estimated temperatures were not significantly related to back-calculated growth. Significant negative effects on back-calculated growth were observed due to increasing air temperatures in the smaller lake, owing to warmer surface waters and a limited amount of preferred cool-water habitat available. A similar relationship was not observed in the larger lake, indicating that the cooler, deeper lake provides ample preferred cool-water habitat for Arctic charr despite climate warming. In addition, young-of-the-year temperatures negatively related to zone 2 growth for the smaller lake, whereas no significant correlation was found for the larger lake. Results here provide evidence for differing climate-influenced growth outcomes depending on the site-specific fish density: preferred thermal habitat volume ratio as dictated by local attributes including lake morphometry, upstream catchment area and life-history strategy. Conclusions from this thesis include the increased need for detailed site- and population-specific assessments of the impacts of increasing temperatures on Arctic charr growth. Better understanding of the drivers of temperature-growth relationships in wild Arctic charr populations will facilitate more accurate stock forecasts with the overall goal of sustaining exploited Arctic charr populations as the climate warms and becomes increasingly variable.

The importance of the cryosphere, and of sea ice in particular, for contaminant transport and redistribution in the Arctic was pointed out in the literature. However, studies on contaminants in sea ice are scarce, and entirely neglect the sea ice geophysical and thermodynamic characteristics as well as interactions between various cryospheric compartments. This thesis addresses those gaps. Ice formation was shown to have a significant concentrating impact on the levels of HCHs in the water just beneath the ice. Both geophysical and thermodynamic conditions in sea ice were shown to be crucial in understanding pathways of accumulation or rejection of HCHs. Although HCH burden in the majority of the ice column remains locked throughout most of the season until the early spring, upward migration of brine from the ice to the snow in the winter has an effect on levels of HCHs in the snow by up to 50 %. In the spring, when snow melt water percolates into the ice delivering HCHs to the upper ocean via desalination by flushing, levels of HCHs in the ice can increase by up to 2 %-18 % and 4 %-32 % for α- and γ-HCH, respectively. Brine contained within sea ice currently exhibits the highest HCH concentrations in any abiotic Arctic environment, exceeding under-ice water concentrations by a factor of 3 in the spring. This circumstance suggests that the brine ecosystem has been, and continues to be, the most exposed to HCHs. α-HCH levels were shown to decrease rapidly in the last two decades in the Polar Mixed Layer (PML) and the Pacific Mode Layer (PL) of the Beaufort Sea due to degradation. If the rate of degradation does not change in the near future, the majority of α-HCH could be eliminated from the Beaufort Sea by 2020, with concentrations in 2040 dropping to < 0.006 ng/L and < 0.004 ng/L in the PML and the PL, respectively. Elimination of α-HCH from sea water takes significantly longer than from the atmosphere, with a lag of approximately two decades.

Because of its geographical location, the Arctic environment is considered as pristine. However, expanding industrial activities in the Arctic require assessment of the toxicity of chemicals at low temperature. Biomarkers defined as &quot;biological responses to a chemical or chemicals that give a measure of exposure or toxic effect&quot; were shown to be relevant to measure in situ impact of oil discharges. Most biomarker studies have been performed with temperate organisms. The Arctic is characterised by low stable temperature, strong seasonality in light, resulting in a short primary production in Spring. Therefore, indigenous organisms have developed specific adaptations to live with a hmited food supply in water near freezing point. Conversely, physical properties of petroleum hydrocarbons are affected by low temperature (i.e. reduced solubility). Consequently, the biological adaptation of cold-water organisms together with the altered oil behaviour, may affect typical biomarker responses. Because oil compounds are strongly prooxidant, the research strategy of this work was based on oxidative stress. The antioxidant defences were investigated by measuring the total oxyradical scavenging capacity (TOSC). The impact of reactive oxygen species was investigated by measuring the stability of the cell membranes. Finally, the physiology of the organisms was considered by looking at heart and respiration rates. Invertebrates were selected for study owing to their abundance in the polar ecosystem. They were sampled using dredges and Scuba diving from the research vessel Jan Mayen (University of Tromso) in May and August 1999, and during May and September 2000 in the l^ords of Svalbard and in Antarctica as well in January 2000. In the Arctic, two bivalves, Mya tnincata and Chlamys islandicus, and two crustaceans, Hyas araneus and Sclerocrangon boreas were selected. In this work, the ecophysiology of Arctic and Antarctic marine invertebrates was investigated and compared to temperate organisms. Polar marine invertebrates are characterised by low respiration and heart rates and a high TOSC. The elevated level of antioxidant defences is thought to reflect the oxidative pressure of the polar marine ecosystem; however, it suggested that a high TOSC may help to protect biomolecules from oxidative damage as repair mechanisms are limited due to the lack of food for 9 months. Organisms were exposed to poly aromatic hydrocarbons either dissolved, dispersed injected or via sediment. TOSC, cell membrane stabiHty and heart rate were valid biomarkers to monitor the impact of poly aromatic hydrocarbons in Arctic marine organisms. The biomarker responses obtained in this study provide essential background information for monitoring the potential impact of oil and gas activities in the Arctic.

The life history of the narwhal Monodon monoceros was studied utilizing animals captured by the Inuit in northern Baffin Island. Segregation by age and sex within this population is evident, with summering groups consisting of mature females with calves, immature and maturing males, and large mature males. The diet consists of arctic cod, shrimp, and squid during June and July, but feeding activity declines markedly during the open-water months of August and September. Growth layers in the unerupted teeth and periosteal zone of the mandible were found to be related to age but absolute rates of accumulation of these layers are uncertain. The maximum life span is estimated to be 40 to 50 years. Male narwhals, which mature sexually at lengths exceeding 390 cm and at 16-17 growth layers, display protracted maturation and a possible annual cycle of spermatogenesis. Females, which mature sexually at lengths exceeding 340 cm and at 12 growth layers, are seasonally polyoestrous, experiencing up to four consecutive ovulations during the breeding season. The gestation period is estimated to be 15.3 months. The season of conceptions is March to May and calving occurs during July and August. Since the lactation period exceeds 12 months, the interval between successive conceptions is usually three years, but about 20% of females conceive at the first breeding season following birth of their calves. The annual population birth rate is calculated to be about 0.07. The basic life history features of the narwhal are similar to those of other medium-sized toothed whales.

No description available.