29 research outputs found
Models of snow distribution patterns for various types of sea ice in the Canadian high Arctic
No full textIn this thesis, the distribution of snow over first-year (FYI), multiyear (MYI) and rubble (RI) sea ice were measured at 15 sites sampled during two years of field research in the Canadian Arctic. A geostatistical technique known as the variogram was used to model the statistical pattern of the snow distribution. The variogram examines the spatial continuity of a regionalized variable and how this continuity changes as a function of distance and direction. Results indicate that the variogram provided a good estimate of the type and change of spatial dependence on the snow depths over the various ice types. Over FYI, the regular smooth ice topography produced a periodicity in the snow drifts that was best estimated using a wave theoretical variogram in combination with a gaussian model. The more irregular ice topography characteristic of MYI and RI produced a more irregular snow drift pattern. The most appropriate models were a combination of the spherical and gaussian variogram models. Geometric anisotropy was present in all 15 sites, indicating a directional trend in the spatial continuity of the snow distribution patterns which was attributed to the prevailing wind vector during depositional storm events. These distribution models were used to estimate the spatial dispersion of the photosynthetically active radiation (PAR) transmittance through the snow and ice covers on the arctic oceans. This application of the models illustrated the importance of snow distribution on the transmittance of PAR. Plots of the transmittance for each ice type were produced. (Abstract shortened by UMI.
Spatial and temporal evolution of snow-covered sea ice, with reference to polar bear habitat
No full textThis 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.May 201
Exploration of grouping characteristics and spatial distribution of beluga whales (Delphinapterus leucas) in the Eastern Beaufort Sea
No full textBeluga whales (Delphinapterus leucas) are considered social whales, but like any other cetaceans, the study of social behaviour is challenging to conduct. Due to the wide distribution of the Eastern Beaufort Sea beluga whale population across its summering grounds, little is known about the large-scale grouping behaviour and spatial distribution of groups. The aim of this research is to explore the grouping characteristics and organization of beluga groups, as well as the habitat preference of different social groups in summer. First, we used aerial photographs captured in July 2019 to describe group size, age composition, inter-individual distance, and swimming direction of beluga groups. We compared characteristics between two key summer habitats: the extended offshore of the Beaufort Sea shelf and the inshore of the Mackenzie Estuary. Results showed that group size and inter-individual distance were similar in both habitats. The average distance in a group varied with age composition and the swimming direction varied between the offshore and inshore. Second, we used GPS locations of beluga sightings recorded by visual observers during aerial surveys conducted in July and August 2019. We investigated the distribution of three beluga social group types (individual belugas, groups of adults, and groups with calf) using hierarchical generalized additive models. The sea surface temperature, bathymetry, and slope described best the summer distribution. Areas of high preference were often associated with prey distribution, suggesting foraging as the main driver of habitat preference. We also hypothesized that body size energy requirements contributed to the variation between the group types. This study revealed for the first-time observations of grouping behaviour in the summer habitat of the Eastern Beaufort Sea beluga whales. Although the results do not reflect the extent and complexity of beluga social behaviour, this study now provides an information baseline for this beluga population. We also encourage multidisciplinary research as an opportunity to further collect data and explore other elements of beluga whale sociality.May 202
A historical analysis of the changes in connectivity and plant cover in Netley-Libau Marsh, Manitoba, Canada: Distinguishing the effects of Lake Winnipeg and Red River hydrology on coastal marsh emergent macrophyte areal extent
No full textNetley-Libau Marsh in Manitoba, Canada is a 26 000 hectare coastal, freshwater marsh located at the mouth of the Red River on the south shore of Lake Winnipeg. Shoreline erosion and loss of emergent vegetation since 1929 has resulted in large expanses of open water and an overall degradation to the marsh ecosystem. Six coastal marshes of similar size and all connected to the south basin of Lake Winnipeg were selected for comparison to determine if marsh vegetation loss is widespread in Lake Winnipeg coastal marshes or limited to Netley-Libau Marsh. As a measure of degradation, open water area measurements of the study marshes were digitized from aerial and satellite images taken between the years of 1929 and 2015. Distinguishing the effects of Red River discharge into the west side of Netley-Libau Marsh from that of Lake Winnipeg regulation was confounded by the finding that direct river connection to the marsh was not firmly established until approximately 1970, just six years prior to the commencement of lake regulation. Red River discharges upstream of Netley-Libau Marsh did not significantly account for variation in open water areal extent within the two Netley-Libau Marsh study areas, nor did modelled Netley Cut discharges. Between 56-95% of the variation in open water areal extent within the six study marshes was explained by two growing seasons of average May-October Lake Winnipeg water levels. Variation in open water areal extent was not comparable in all six study marshes and the frequency and duration of low-water periods decreased after 1976. My findings show that the loss of habitat complexity and emergent vegetation in Lake Winnipeg coastal wetlands has been ongoing since the early 20th century and is attributed most heavily to the decrease in low-water periods in Lake Winnipeg levels. The greatest loss of open water area within Netley-Libau Marsh occurred in years when average Lake Winnipeg water surface elevation decreased to 217 metres above sea level during typical ice-free months (May-October). These findings highlight the importance of periodic lowering of Lake Winnipeg water levels in promoting coastal marsh vegetation growth and future habitat restoration efforts.May 201
Monitoring beluga whales from space: estimating abundance and evaluating social structure using VHR satellite imagery
No full textImproving monitoring efforts of Arctic species is becoming increasingly important given the rate of change in Arctic marine ecosystems and the presumed impact on Arctic marine mammals, such as beluga whales (Delphinapterus leucas). Very High Resolution (VHR) satellite imagery is emerging as a promising tool for efficiently monitoring beluga whale populations, which can be logistically challenging with current methods. Here we use VHR satellite imagery to investigate two conservation relevant aspects of beluga whale populations: abundance and social dynamics. First we determined two missing pieces of information required to estimate beluga whale abundance in VHR satellite imagery: 1) depths that beluga whales are visible in VHR satellite images, which are used to define availability bias correction factors, and 2) a comparison of abundance estimates in VHR satellite imagery to current aerial methods. We determined that beluga whales can be detected only at the surface in turbid water and at depths of 0 – 2 m in clear water in 0.31 m resolution VHR imagery, and that beluga whale availability bias corrected abundance estimates made from synchronous VHR satellite imagery and drone surveys were comparable. We further used VHR imagery to describe beluga whale group size, composition, and cohesion in beluga whale populations from Cumberland Sound, Eastern High Arctic – Baffin Bay, and Western Hudson Bay in relation to anthropogenic disturbance, density, and social context. We found that group size decreased with harvest, which seemingly reflects population decline or removal of key social individuals, while recent increases in vessel traffic were associated with larger group sizes and greater spatial cohesion, possibly suggesting an adaptative response to increase vigilance to vessel disturbance. Beluga whale social cohesion was mainly influenced by the presence of juvenile whales, with adult-juvenile mixed groups having smaller inter-individual distances than groups with adults only. Future beluga whale management efforts may benefit from incorporating VHR imagery into research programs and continuing to assess beluga whale social group dynamics alongside traditional abundance estimates; particularly given the expansion of anthropogenic disturbance in the Arctic.October 202
Development of a small-scale approach to assess sea ice change using weekly ice charts, with application to Anguniaqvia Niqiqyuam Marine Protected Area
No full textBroad-scale changes in sea ice have been documented across the Arctic; however, less is known about sea ice decline at smaller scales, focused at high-priority areas such as marine protected areas (MPAs) or places identified as important by Indigenous Peoples. Here, we develop a small-scale application of assessing sea ice change using weekly sea ice charts and apply that to assess sea ice change in Anguniaqvia Niqiqyuam MPA (ANMPA) from 1980 to 2019. Over that 40-year period, sea ice coverage in ANMPA decreased and open water increased by approximately a month (31.6 days at 50% ice; 33.8 days at 20% ice remaining during break-up and 80% ice formed during freeze-up). Break-up has gone from occurring in mid- or late July to occurring in late June or early July. Freeze-up has changed from occurring in mid-October to occurring in early November. As sea ice decline may have dramatic impacts for the ecosystem and consequences for the people that rely on this important area, we highlight the need to better understand the impacts of sea ice decline in small-scale priority places and also contribute to the development of community-scale approaches to increase the accessibility of assessing change
Long-term Trends in the Population Ecology of Polar Bears in Western Hudson Bay in Relation to Climatic Change
No full textFrom 1981 through 1998, the condition of adult male and female polar bears has declined significantly in western Hudson Bay, as have natality and the proportion of yearling cubs caught during the open water period that were independent at the time of capture. Over this same period, the breakup of the sea ice on western Hudson Bay has been occurring earlier. There was a significant positive relationship between the time of breakup and the condition of adult females (i.e., the earlier the breakup, the poorer the condition of the bears). The trend toward earlier breakup was also correlated with rising spring air temperatures over the study area from 1950 to 1990. We suggest that the proximate cause of the decline in physical and reproductive parameters of polar bears in western Hudson Bay over the last 19 years has been a trend toward earlier breakup, which has caused the bears to come ashore in progressively poorer condition. The ultimate factor responsible for the earlier breakup in western Hudson Bay appears to be a long-term warming trend in April-June atmospheric temperatures.De 1981 à la fin de 1998, la condition physique de l\u27ours polaire adulte, mâle et femelle, s\u27est détériorée de façon importante dans l\u27ouest de la baie d\u27Hudson, tout comme le nombre de naissances et la proportion d\u27oursons de l\u27année pris durant la période d\u27eau libre, et qui étaient indépendants au moment de leur capture. Au cours de la même période, la débâcle de la banquise sur l\u27ouest de la baie d\u27Hudson s\u27est produite plus tôt. Il existait un lien très marqué entre le moment de la débâcle et la condition physique des femelles adultes (c.-à-d. que plus la débâcle se produisait tôt, plus les ourses étaient en mauvaise condition physique). La tendance à une débâcle précoce était également corrélée à l\u27augmentation de la température ambiante printanière dans la zone d\u27étude de 1950 à 1990. On suggère que la cause immédiate du déclin des paramètres physiques et reproducteurs de l\u27ours polaire dans l\u27ouest de la baie d\u27Hudson au cours des derniers 19 ans a été une tendance à une débâcle précoce, ce qui amené les ours à venir sur la terre ferme dans un état de plus en plus mauvais. Le facteur responsable de la débâcle précoce dans la baie d\u27Hudson semble être en fin de compte la tendance au réchauffement à long terme de l\u27atmosphère en avril et en juin
A semi-automated method using object-based image analysis (OBIA) to detect and enumerate beluga whales in summer from very high-resolution (VHR) satellite imagery
No full textBeluga whale habitat selection and distribution in the Mackenzie Estuary and the Tarium Niryutait Marine Protected Area
No full textThe Eastern Beaufort Sea (EBS) beluga population migrates to the Mackenzie Estuary and to the Tarium Niryutait Marine Protected Area every summer and the reasons behind this selection are not fully understood. Once in the Estuary, beluga whales (Delphinapterus leucas) are harvested by Inuvialuit communities of the Inuvialuit Settlement Region for whom they represent an essential country food, contributing to their well-being. In the last decade, community members voiced their concerns and identified research priorities pertaining to belugas resources, baselines and habitats. To enhance our understanding of EBS beluga whale habitat and further anticipate effects of a changing climate, it was crucial to understand why belugas select these habitats. We created a habitat model based on aerial surveys observations from the late summer 2019 paired with remote sensing imagery to establish a baseline of environmental and spatial conditions selected by belugas. Then we assessed the baseline against historical data. We finally evaluated the habitat model with concurrent tagged observations to integrate the inferences made at a larger spatio-temporal scale. High turbidity and warm water temperatures were the two most important factors explaining beluga presence and were associated with the inshore waters of the Mackenzie River channels and along unprotected coastlines. Comparisons with past observations suggested that the observed beluga distribution had shifted from the baseline and was probably the results of the influence of changing environmental conditions on beluga response, either on a temporary (i.e., acclimatisation) or permanent basis (i.e., adaptation). The evaluation of the habitat model showed mixed results. The inferences of selection, created in combining quality of environmental conditions and belugas mechanisms of selection, explained the intertwined patterns of beluga habitat distribution. Those findings enhanced our understanding of EBS beluga ecology and highlighted the complexity in defining and predicting beluga habitat distribution. This complexity, by preventing an accurate assessment of the changing beluga habitat distribution, represents new challenges for harvesters that who may have to switch the timing and location of their harvest in response.May 202
