Impacts of stratified environmental flows upon the distribution of sediment and biology in lakes and the coastal ocean

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A key feature of almost all lakes and coastal seas is that they are density stratified, with lighter water floating above the deep denser layers. This stratification has critical consequences for sediment deposition, under-ice circulation, and fish habitat. However, substantial questions remain about the fundamental fluid dynamics controlling stratification and mixing in Canadian waters. In order to accurately interpret sedimentary records, we need to know how stratification in coastal seas changes where sediment from a river is deposited. To investigate the food chain under the ice in the frozen lakes of Canada, we need to understand the impact on mixing principles of the inverted, winter stratification that occurs when water is between 0-4 Celsius. To identify where fish dwell in lakes during summer, we need to understand how internal waves in thermally-stratified layers affect the regimes of cold blooded animals. This proposal will determine fundamental physical processes of stratification of significant geological, ecological, and economic importance to Canada. To address real-world stratification problems, the applicant and team will use an innovative combination of laboratory fluid dynamics experiments, theory, modelling and field observations in three different environmental systems. We will employ novel lab experiments and field studies on the Fraser River in BC to quantify how convection controls particle sedimentation rates from river plumes, providing a conceptual framework to understand sediment transport from the land to the ocean. Fieldwork on frozen lakes in southern Ontario will probe under-ice circulation patterns to elucidate the consequences of changing thermal and light conditions upon winter food chains. Our deeper physical understanding of winter inverse stratification will then drive new collaborative work with investigators in other Northern countries. Finally, the proposed work will determine the influence of internal waves in stratified lakes upon fish species distribution, capitalizing on the very large acoustic fish telemetry datasets available for Lake Ontario and building on existing collaborations with fisheries scientists. Taken together, this research is essential and urgent to improve our understanding of how our many stratified lakes and marine systems function. These efforts will train at least 20 HQP in an environment committed to inclusion. They will receive high-level training in environmental fluid dynamics, lab and field-based studies, as well as in developing theory and in performing data analysis that will prepare them for a broad range of opportunities in academia, government or private industry. Ultimately, my research program on environmental fluid dynamics will identify how sediment and biology distributions in different water bodies could shift as the warming climate changes the density stratification of these systems.