The impacts of climate change on thermal stratification and dissolved oxygen in the temperate, dimictic Mississippi Lake, Ontario

This study investigates and reports the climate change's effects on the Mississippi Lake thermal structure and dissolved oxygen (DO) for baseline (1986-2005) and future (2081-2100) periods. Future meteorological vari-ables were derived from the second-generation Canadian Earth System Model (CanESM2) under three emission scenarios (RCP2.6, RCP4.5, and RCP8.5). The long-term lake inflow was modelled using the Thornthwaite monthly water balance model (TMWB) coupled with an Artificial Neural Network (ANN) to simulate the water level in the lake. Several methods were analyzed to assure the above is the best for estimating the water budget in this region. The water quality of Mississippi Lake was analyzed using a calibrated CE-QUAL-W2 model for the years 2017 and 2018. A major challenge in setting up the model was limitations in some essential water quality indicator inputs, which were estimated using reliable experimental relationships. Our results show that the baseline average surface water temperature of 14.6 degrees C would increase by 1.31 degrees C, 1.34 degrees C, and 2.69 degrees C under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. In contrast, the baseline average hypolimnetic DO of 7.1 mg/L would decrease by 1.4%, 6.2%, and 14.3% in RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Such a rise in water temperature and the consequent diminishment of DO in deep waters would threaten the future sustainable growth of warm-water fish species in Mississippi lake.