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Assessing projected riverine and lakeshore heatwaves: examining rates of change and ecological consequences in the Great Lakes region
Tillotson, Brooke M.
Tillotson, Brooke M.
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2025
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Abstract
Increasing water temperatures have been linked to higher fish mortality in lakes and rivers. As anthropogenic climate change raises air temperatures, riverine and lakeshore heatwave events are expected to increase in intensity and frequency. A gap exists in year-round heatwave projections for a connected river-lake system. Using the FutureStreams dataset, we projected heatwave intensity, frequency, duration, and onset rates to 2100 in the Great Lakes region using four Representative Concentration Pathways (RCP) derived from three General Circulation Models (GCM). We examined seasonal differences in heatwave parameter projections, dissolved oxygen predictions, and temperature tolerances and preferences for several Great Lakes region fish species to determine the extent to which each RCP will affect fisheries. Heatwave occurrences year-round, as well as extreme severity events are expected to grow. Heatwave predictions can help prepare climate mitigation and adaptation solutions of Great Lakes fisheries. Greatest increases in heatwave intensities are observed during summer. Species with lower temperature tolerances are most at risk, especially as the heatwave max temperature and duration increases raise oxythermal stress. Under the GCM ensemble mean high emissions scenario (RCP 8.5), model simulations project summer riverine and lakeshore heatwaves to increase by as much as over 30 days per decade. Annual mean river temperature anomaly is expected to be an additional 6 degrees at the end of the century. The worst-case scenario also limits oxygen saturation to 8 mg/L in summer and 10 mg/L in fall. The best-case scenario limits annual mean river temperature anomaly to under 2 degrees. Further research should evaluate the efficacy of emissions reductions and river habitat restoration to understand mechanisms to limit heatwave risk and subsequent ecological mortality.
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