Long-term hydroclimate trends in the Great Lakes basin: Are there hotspots of regional change?

The Laurentian Great Lakes basin This study analyzed key hydroclimate components across the entire Laurentian Great Lakes basin, one of the largest freshwater basins on Earth and home to roughly 20% of all fresh, unfrozen surface water. The hydroclimate components analyzed included surface air temperature, precipitation, evapotranspiration (ET), snow water equivalent (SWE), runoff, and surface soil moisture from 1951 to 2020. Hydrological variables were simulated using regional customization of the Weather Research and Forecasting hydrological model (WRF-Hydro), and changes in the annual magnitude and seasonal variability (i.e. seasonality) of all variables were assessed. Our findings reveal significant spatial and temporal variations in hydroclimate variables across the basin. The Great Lakes basin is experiencing noteworthy changes in hydroclimate variables, including pronounced rises in surface air temperature, ET, and runoff (low flow), as well as declines in SWE. The distinct spatial patterns of changes in magnitude and seasonality are identified throughout the region. For instance, the Superior basin exhibits unique hydrological patterns, including an earlier peak in SWE and decreased high flow, both of which are influenced by its unique climatic and geographical conditions. This long-term analysis of hydroclimate trends provides valuable insights into historical hydrological changes and their implications for future conditions in the Great Lakes basin, emphasizing the need for localized studies and targeted management strategies. • We investigated long-term hydroclimate changes in the Great Lakes basin. • Surface air temperature increased in magnitude but maintained its seasonal variability. • Precipitation exhibits non-significant changes in both magnitude and seasonal variability. • Hydrological variables except SWE increased in magnitude but decreased in seasonal variability. • The findings underscore the need for region-specific climate adaptive management.