Application of hydrodynamic models in simulating the thermal regime of Lake Superior.

摘要

In large systems, such as the Great Lakes and coastal oceans, physical processes have a significant influence on chemical and biological phenomena. Hydrodynamic modeling assists in describing these physical characteristics and in recent years, these models have been extensively applied in the Great Lakes basin to study the response of the lake ecosystem to long-term meteorological forcing conditions. Due to its role in mediating physical, biological and chemical processes in lake environments, water temperature (and the attendant thermal regime) has been the parameter of interest in many of these mathematical modeling studies and was adopted as the primary metric for this research. Owing to its pristine waters and relatively undisturbed (lowest-urban-impact) watershed, Lake Superior, the largest, deepest and northernmost of the Great Lakes, was selected as the study site for this doctoral work.;This study first describes the calibration and confirmation procedure for a three-dimensional (3D) hydrodynamic model developed for the western basin of Lake Superior, with an emphasis on evaluating model performance using a multi-criteria approach, and the introduction of a new goodness-of-fit criterion that finds applicability in an ecological context. The following segment introduces a one-dimensional (1D) hydrodynamic framework, adapted to explore spatio-temporal patterns in thermal stratification in Lake Superior (large lakes), supporting the development of coupled 1D frameworks to provide a computationally efficient and accurate approach to parameterize and test complex 3D ecosystem models. This 1D hydrodynamic model was further applied, in conjunction with field measurements of water temperature, to identify differences in the response of the thermal regime of Lake Superior in the nearshore and offshore regions to the divergent forcing conditions in the unusually warm year (2012) and the extreme cold year (2014).