Previous studies of cooling igneous plutons did not consider the possible influence of sloping surface topography. Topographically-driven fluids in high relief terrain, however, are thought to interact with deep buoyancy-driven fluids to produce large lateral-flow systems up to 5 km long and 20 km long in silicic and andesitic volcanic terrain, respectively. In this study, a quantitative investigation of the interaction of topographically-driven and buoyancy-driven fluid flow is conducted through the use of a finite element numerical model to simulate the fluid flow and thermal regimes associated with a cooling igneous pluton in the presence of significant topographic relief. The system considered in this study is that of a pluton with dimensions 2 km by 3 km and an initial temperature of 980 °C centered beneath a mountain having relief of 1 km over a horizontal distance of 3 km. Simulation results indicate that the topographic component of flow interacts with buoyancy to produce two separate flow systems, a shallow topographically-driven flow system and a deeper convecting system. The resulting hydrothermal system evolves in a more complicated fashion than in flat topography cases. In addition, the existence of the shallow topographically-driven flow system partially masks the presence of the heat source by preventing fluids having the chemical signature of the deeper, hotter environment from reaching the surface. Cooling rate of the pluton is also increased and boiling is inhibited. These effects, however, are primarily a result of the pluton being injected into a cooler host rock. The host rock is cooler in the sloping topography case due to advective cooling prior to pluton injection. Model results also indicate that temperature beneath the mountain and the position of the zone of mixing remain relatively constant for almost 50,000 years. The stability of the temperature conditions and the position of the zone of mixing may increase the likelihood for the deposition of epithermal ore bodies in this region.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.

Les organismes aquatiques sont adaptés à une grande variabilité hydrique et thermique des rivières. Malgré ceci, la régulation des eaux suscite des changements aux débits qui peuvent provoquer des impacts négatifs sur la biodiversité et les processus écologiques en rivière. Celle-ci peut aussi causer des modifications au niveau des régimes thermiques et des caractéristiques de l’habitat du poisson. Des données environnementales et biologiques décrivant l’habitat du poisson existent, mais elles sont incomplètes pour plusieurs rivières au Canada et de faible qualité, limitant les relations quantitatives débit-température-poissons à un petit nombre de rivières ou à une région étudiée. La recherche menée dans le cadre de mon doctorat concerne les impacts de la génération d'hydroélectricité sur les rivières; soit les changements aux régimes hydriques et thermiques reliés à la régulation des eaux sur la variation des communautés ichtyologiques qui habitent les rivières régulées et naturelles au Canada. Suite à une comparaison d’échantillonnage de pêche, une méthode constante pour obtenir des bons estimés de poisson (richesse, densité et biomasse des espèces) a été établie pour évaluer la structure de la communauté de poissons pour l’ensemble des rivières ciblées par l’étude. Afin de mieux comprendre ces changements environnementaux, les principales composantes décrivant ces régimes ont été identifiées et l’altération des régimes hydriques pour certaines rivières régulées a été quantifiée. Ces résultats ont servi à établir la relation significative entre le degré de changement biotique et le degré de changement hydrique pour illustrer les différences entre les régimes de régulation. Pour faire un complément aux indices biotiques déjà calculés pour l’ensemble des communautés de poissons (diversité, densité et biomasse des espèces par rivière), les différences au niveau des guildes de poissons ont été quantifiées pour expliquer les divers effets écologiques dus aux changements de régimes hydriques et thermiques provenant de la gestion des barrages. Ces derniers résultats servent à prédire pour quels traits écologiques ou groupes d’espèces de poissons les composantes hydriques et thermiques sont importantes. De plus, ces derniers résultats ont servi à mettre en valeur les variables décrivant les régimes thermiques qui ne sont pas toujours inclues dans les études hydro-écologiques. L’ensemble des résultats de cette thèse ont des retombées importantes sur la gestion des rivières en évaluant, de façon cohérente, l’impact de la régulation des rivières sur les communautés de poissons et en développant des outils de prévision pour la restauration des écosystèmes riverains. / Widespread anthropogenic impacts to river ecosystems are currently changing the naturaly variability of flow and temperature regimes, with potentially important repercussions on the stability and function of aquatic communities. Although fish community responses to flow alterations from river regulation have been quantified in the past (e.g. late maturation of salmonid populations due to attenuated flows or stranding of fishes from down-ramping flows), the scarcity of high quality, long-term data, especially in Canadian rivers, has limited our understanding of the effect this has had on other environmental drivers and fish community structure across this heterogenous landscape. Using extensive field surveying across unregulated and regulated rivers in Alberta, Ontario, Québec, and New Brunswick coupled with data from national, provincial, and private flow and water temperature gauge networks, I showed the effects of flow and thermal regimes on fish diversity, density, biomass, and different types of ecological guilds. I also examined the extent to which different regulation practices have modulated the response of riverine fish to the combined effect of changes to flow and thermal regimes. To first establish a methodology for quantifying fish community structure across rivers, I generated reliable site-specific species richness, density, and biomass metrics that combined measures from two commonly used surveying methods. To then quantify the response of these fish community metrics to river regulation, I defined daily and hourly flow indices based on river flow conditions, developed hydrologic regime variables that described dominant patterns of flow variation, and calculated flow alterations based on the difference in multivariate space of these hydrologic regime variables for regulated rivers from reference flow conditions. By applying this same approach to fish community metrics, I identified a significant positive relationship between biotic and flow alterations and showed a separation between the two most distinct flow regulation types, run-of-river (ROR) and hydro-peaking. To tease apart the relative importance of each environmental driver for establishing fish communities across river regimes, I provided quantitive thermal indices based on river water temperatures and developed thermal variables akin to those described for flow regimes. To evaluate whether quantitative fish guild estimates, rather than total river biomass or density estimates, would respond more strongly to river thermal regimes, I compared the response of different types of fish guilds to flow and thermal regimes across rivers, including those subjected to river regulation. All fish guild models performed better relative to studying total river estimates, confirming the use of trait-environmental relationships for studying fish community responses across rivers. I also found that integrating thermal regimes in hydro-ecological studies is critical in predicting fish guild responses across rivers. Collectively, these findings have important repercussions for river management, as they provide comprehensive assessments of the environmental variables driving fish community responses, inform the potential range of ecological consequences of anthropogenic alterations on natural flow regimes, and contribute to establishing more transferable predictions for restoring impacted rivers. More broadly, the thesis results are important given future global climate warming, its synergistic effects with other anthropogenic stressors, and ongoing scarcity for water and energy sources.

The evolving science of astrobiology for the search for life beyond Earth has put focus on the possibility of subsurface bodies of liquid water beneath the surface of icy moons within our Solar System. Specifically, the Jovian moon of Europa and the Saturnian moon of Enceladus show telling characteristics of endogenous heating through their complex tidal resonances with their parent planets – suggesting the presence of oceans of liquid water and therefore a potential for astrobiology. Today, the planning of upcoming satellite missions to guarantee the identification of completely unknown, possibly habitable environments has become an intriguing task for space agencies worldwide. A method of guidance, ground-truthing, debugging and testing of the viability of planned satellite missions is to utilize relatively accessible analogue environments on the Earth. Fortunately, the research of Antarctic subglacial water environments has been acknowledged as the most suitable analogues to the environments of Europa and Enceladus. Given its recorded motions of ice dynamics, erosion, complex thermal systems, and occasions of sampled microbes within – these sensitive, exotic environments beneath the Antarctic ice bed are currently assessed for their suitability as habitats for extremophilic microorganisms, which may provide important insights into the potential existence of habitats, perhaps even life, on icy moons. Ultimately, viable lessons can be drawn from the research of Antarctic subglacial environments given the uncovering of reliable sanitary methodologies that are going to be required during future approaches and sampling of natural systems of extraterrestrial subglacial environments in order to minimize irreparable anthropogenic disturbances on any potential astrobiology. Regardless of the question if the future investigation of Europa’s and Enceladus environments is going to reveal astrobiology within beneath their icy surfaces; this investigation is going to be of invaluable information for the improving familiarity of physical systems beyond Earth. / Sedan länge har forskare vetat att flytande/rinnande vatten är en av de viktigaste förutsättningar för allt liv på Jorden. Under de senaste decennierna har frågan om liv på Jupiters måne Europa, och Saturnus måne Enceladus aktualiserats, efter upptäckten av frusna islager på deras månytor. Evidens från respektive månars omloppsbanor, gör att forskare idag tror att månarnas djupa islager hettas upp inifrån av en aktiv, inre geologi, vilket i sin tur kan tyda på större mängder av flytande vatten. I och med omvandlingen av is till flytande vatten, får detta forskare att tro att cirkulationen av vatten, ihop med den aktiva geologin, möjligtvis har skapat och upprätthåller beboliga förutsättningar för mikroskopiskt liv. I dagsläget planeras ett flertal satelliter skjutas upp till månarna med uppdrag att bekräfta fallet om flytande vatten och beboliga miljöer på månarna, och därmed även undersöka frågan om månarna möjligtvis bär på liv. På den frusna kontinenten Antarktis har ett flertal motsvarande subglaciala miljöer undersökts för att fastställa deras kvalifikationer att upprätthålla liv under extrema levnadsförhållanden. Under dessa undersökningar har ett flertal mikroorganismer påträffats i prover från iskärnor från två subglaciala sjöar (Vostoksjön och Whillanssjön), varav några blivit omstritt påstådda som inhemska extremofiler. Ifall detta stämmer, betyder det att de två subglaciala sjöarna underhålls av ett unikt samspel av drivande faktorer som upprätthåller de nödvändigaste levnadsförutsättningarna för att mikroorganismer kan överleva, även frodas i uppenbart extrema miljöförhållanden. Med forskningen av Antarktis subglaciala sjöar som rapporterar ett unikt samspel mellan is, vatten och underliggande geologi; kan den fortsatta fastställningen av detta fysiska samspel, samt vidare identifikationer av inhemska mikroorganismer att bli en viktig lärdom för framtida satelliters datainsamling av subglaciala vattenmiljöer på Europa och Enceladus. För att underlätta och effektivisera sökandet efter potentiella livsmiljöer, samt möjligtvis hitta utomjordiskt liv på isiga månar bör framtidens satellituppdrag dra stor lärdom och väga in de erfarenheter och resultat som gjorts på subglaciala sjöar i Antarktis.