Climate change is impacting high latitude regions disproportionately more than those at a lower latitude. With polar lakes being highly sensitive to changes in the climate, shifts in lake ice dynamics and hydrodynamics are indicators of such changes in regional and global climates. These changes impact future seasons in a positive feedback loop, where changes in winter ice cover impact open water nutrients levels and lake thermal structure. This highlights the importance for long-term monitoring. Despite the abundance of lakes distributed across Northern Canada, there has been limited research conducted on these sentinels of climate change. Specifically, Great Bear Lake (GBL), the largest lake entirely within Canada’s boarders is of great ecological importance and a vital resource for the Délı̨nę Got’ı̨nę community. Due to the lakes large size (Surface Area = 31, 153 km2) and extreme climate, there has been little research conducted on the lake. Winter research is limited to non-intrusive methods of modelling and remote sensing assessing the ice phenology and ice thickness. In-situ measurements taken to assess the lakes hydrodynamics are limited and even with extensive datasets it is difficult to represent the entire lake. The purpose of this research is to deepen our understanding of the current hydrodynamic conditions of GBL by implementing a 3-D Hydrodynamic Numerical Model the Aquatic Ecosystem Model (AEM3D) from August 2023 – 2024. The model is validated with 3 datasets of in-situ water temperature measurements to ensure accurate model outputs. AEM3D captures surface temperatures well (RMSE = 3.08°C, MBE = -0.30°C), subsurface temperature profiles measured with a Conductivity, Temperature, Depth sensor (CTD) are better depicted (RMSE = 1.45°C, MBE = 0.40°C). A year-round mooring located on the outer edge of Keith’s arm provides long term monitoring with similar timings in cooling (4°C) events between the modelled and measured temperature profile. Preliminary investigation into modelled temperatures and velocity was discussed. Stratification is seen developing in the sheltered shallow arms of the lake, with weak stratification seen in the center of the lake. A strong wind event in October 2023 is used to show the velocity and temperature changes in Smith and Keith Arm, demonstrating the benefits of 3-D modelling. This research provides a baseline model set up and preliminary assessment of the current conditions of GBL. Therefore, this study can aid in management strategies to help mitigate the effects of climate change on this large lake. Similarly, this study shows the first time that AEM3D has been applied to a large northern lake and can further highlight the benefits of 3-D lake modelling to capture complex hydrodynamics of a large lake in northern Canada.
Kirin Lorente (Thu,) studied this question.