Climate, Chemistry and the Great Lakes: What Goes Up Must Come Down
The Laurentian Great Lakes can influence regional climate and chemistry through a variety of mechanisms. First, I'll discuss the atmospheric moisture budget in the Great Lakes region using reanalysis and future climate model data to develop a process-level understanding of the precipitation seasonality. We identify the lakes not only as a source of moisture, but also in generating localized moisture flux convergence/divergence patterns that induce differences in the water cycle seasonality. Despite differences in historical simulations from the Coupled Model Intercomparison Project (CMIP6) data archive, common patterns of change are present in the future projections of climate variables. Specifically, summer drying and winter/spring wetting by mid-century is consistent across models, indicating a shift in the precipitation seasonal cycle towards colder months, while evapotranspiration magnitudes revealed unambiguous increases throughout the year in all models. Overall, the atmospheric transport of moisture is the primary driver of future precipitation changes, with an amplification of the moisture flux convergence seasonal cycle in future climate model simulations . Second, I'll discuss the role of the lakes as a source or sink for chemical constituents in the atmosphere, ranging from the emission of lake spray aerosol and their role in regional chemistry and climate, as well as deposition of aerosols to the lakes as a means of altering lake composition. Finally, I'll discuss these interactions from the perspective of what goes up (e.g., water via evaporation, aerosols via lake spray) versus what comes down (e.g., aerosol deposition of nutrients, precipitation).
