Approximately 7000 to 8000 years ago when Hudson Bay became ice-free the Tyrrell Sea flooded the Hudson basin and deposited fine grained marine sediments overlaying the previous glacial tills. Coincident with the ablation of the ice sheet isostatic rebound occurred causing regression of the Tyrell Sea and the emergence of a flat, relatively impermeable surface that would eventually host one of the world’s largest wetlands: the Hudson Bay Lowlands. The low permeability marine sediments and low regional slope reduced recharge and runoff, respectively, so that basal tidal marshes were established, and with isostatic up lift were eventually replaced by swamp forests and then forested and non-forested bogs. Recent discovery of kimberlite (diamondiferous) pipes in an area of the lowlands has led the development of an open-pit diamond mine which requires dewatering of the regional aquifer. Dewatering is depressurizing the surrounding Silurian bedrock that underlies the marine sediments. It was hypothesized that these marine sediments would act as a confining layer, isolating the overlying peatlands from the regional bedrock aquifer. We tested this hypothesis by instrumenting a 1.5 km long transect located within the zone of the mine’s influence that crossed various bogs and fens overlying these marine sediments, and was anchored at both ends by bedrock outcrops (bioherms), which represented areas of no marine sediment. Along this transect wells and piezometers were installed within the peat profile and upper marine sediments and bedrock to determine changes in water table and hydraulic head. The exposed bedrock outcrops (bioherms) did act as local drainage nodes, however, this effect was limited to ~30 m, beyond which water tables and hydraulic heads were similar to a control site located 25 km away. However, within this 30 m zone daily losses of water by the enhanced recharge often exceeded those of evapotranspiration (~3mm/day) representing a major local loss of water to the system. It is the distance to bedrock, rather than distance to bioherm, that determines strength of recharge. In areas of thinner marine sediments the daily fluxes were similar (but less) than those in the areas directly surrounding the bioherms, despite being 100s of meters away from the bioherms. The stratigraphy surrounding the bioherms lead to complicated flow regimes with higher conductivity layers (e.g., sands) circumventing the lower permeability marine sediments which may help extend the effect of the bioherms beyond the 30 m distance. The drying peat around the bioherms, and the elevated nature of the bioherms in a flat landscape, put them at increased risk for lighting strikes and thus fires; however, very little viable fuel exists in the peatlands around the bioherms and any fires that might occur would be confined to the bioherm and not spread into the surrounding peatland. Overall, at least within the first 5 years of aquifer dewatering, seasonal weather played the dominant role in affecting the hydrology of the peatlands; a heavy snow pack and cool, wet summer can mask, or at least minimize the effects of aquifer dewatering.

Rapidly changing climates in northern Canada make the western Hudson Bay region an area of high importance for paleoenvironmental studies. Long-term changes in assemblages of diatoms (microscopic algae) were analyzed from lake sediment cores from Baker Lake, Nunavut, and Lake AT01, northern Ontario, to track responses to past environmental changes. Diatom assemblages dating to 6700 years ago in AT01 were initially characterized by cold- tolerant Fragilarioid assemblages, but shifted to an assemblage dominated by large benthic species and Cymbella diluviana consistent with the timing of the Holocene Thermal Maximum after 6300 years BP. A possible drainage event in Lake AT01 may have added significant hydrologic control on the diatom assemblages. The post-industrial period is marked by the largest compositional shifts in both records. Assemblages during the 20th century are indicative of reduced ice cover and enhanced thermal stratification linked to a climate regime shift noted in Hudson Bay since the mid-1990’s.

Thesis (D. Min.)--McCormick Theological Seminary, 1995. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 829-838).

Proefschrift Erasmus Universiteit Rotterdam. / Bibliogr.: p. 150-159. - Met samenvatting in het Engels en Nederlands.

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The Hudson River estuary (HRE) is a well monitored aquatic resource and much secondary data exist for this system. We developed two objectives based on accessible HRE aquatic data. The first objective was to determine if changes in HRE fish community over the time period (1974 to 2005) years are correlated to local and regional climate. We addressed this objective by employing a multivariate statistical approach. We confirmed that the HRE fish community structure has changed over the time period (1974 to 2005). These changes are correlated with local hydrology (freshwater flow and water temperature) and regional climate (Atlantic Multidecadal Oscillation or AMO and North Atlantic Oscillation or NAO). We found that abundances of striped bass larval stages are positively correlated with high freshwater flows and juvenile shad abundances are negatively correlated with the AMO or warmer sea surface temperatures (SST). This finding suggests that climate-related variability affects HRE juvenile shad abundances and current management strategies for this declining species should include the implications of climate change. The second objective was to examine whether factors such as sediment type, water characteristics and distance to nearest submerged aquatic vegetation (SAV) beds affect the occurrence or presence/absence of juvenile American shad (Alosa sapidissima) and juvenile striped bass (Morone saxatilis) in the HRE during the fall. We addressed this objective by applying geostatistics and general linear mixed effects models. We found the probability of presence for both species were commonly driven by spatial dependence or river mile, Julian day and salinity. Our results include maps depicting probability of occurrence (or presence) for both species throughout the HRE. We found the highest predicted probabilities of juvenile American shad presence are found in the Upper HRE. Conversely, highest predicted probabilities of juvenile striped bass presence are found in the Lower HRE. Habitat partitioning between these two species is present during the fall in this system but the mechanism is unclear. Future studies could address a possible predator-prey or competitive relationship between juvenile American shad and juvenile striped bass.

<p> This study focuses on the relations hip between ice cover and wind frequency, wind speed and air temperature. Results showed that there are four distinct MELT periods along the west coast of Hudson Bay. With a standardized MELT period, stations are generally higher correlated with their southern neighbours. Onshore wind frequencies increased signficantly from the NOMELT to the MELT period, and were associated with air temperatures 3 to 4 degrees Celsius colder than those of offshore winds. </p> <p> Mean air temperature was most highly correlated with percent ice cover. Ice cover was most strongly correlated with mean air temperature at Chesterfield Inlet and least so at Churchill. Thus, freeze-up and melt at Chesterfield Inlet are most strongly influenced by air temperature whereas at Churchill, other factors, presumably wind direction and currents, strongly influence the ice cover. Ice cover was most strongly influenced by air temperature during the NOMELT period. This shows that cold temperatures hasten freezeback more than warm temperatures hasten MELT. </p> / Thesis / Bachelor of Arts (BA)

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