Watershed controls on Lake chemistry

Our group on Remote Sensing of Water Resources at University of Minnesota is working to produce maps of remotely sensed CDOM, chlorophyll-a, and suspended sediment in 10,000+ lakes across MN and parts of WI and MI. With such a rich dataset, I am exploring what watershed characteristics control the wide variety of lake types within this geographic region. Wetlands and land cover, lake connectivity, and lake morphology all influence CDOM, and can limit the reliability of CDOM as proxy for DOC (Griffin et al., 2018b).

Time Series analysis of CDOM

Using Google Earth Engine, our remote sensing algorithms developed recently can be applied to historical Landsat imagery dating to the 1980s. Other boreal and north temperate regions, particularly the Northeast USA and Scandinavia, have shown increases in DOC and CDOM over the past thirty years, but this has not been well constrained for the Upper Midwest. Preliminary time series analyses show little unidirectional change in CDOM in our study area, however, possibly owing to differences in acid rain impacts and climatic change compared to the NE and Scandinavia.