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Webinar: Spatial variability and potential long-term trends in Great Lakes carbon

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Wednesday, 25 January 2017, 10:30

Wednesday, January 25, 2017. 10:30 AM. Webinar: Spatial variability and potential long-term trends in Great Lakes carbon. Galen A. McKinley, University of Wisconsin, Madison, Atmospheric and Oceanic Sciences and Center for Climatic Research. Sponsored by Cooperative Institute for Limnology and Ecosystems Research. More information here.


Biogeochemical and carbon cycling in Great Lakes occurs in the context of a highly variable aquatic landscape that is significantly impacted by physical forcing. In order to understand biogeochemical cycling in its mean state and as it changes, we must quantify the role of physical variability in space and time. Here, three carbon cycle examples will be presented. In Lake Superior, analysis of a coupled hydrodynamic-biogeochemical model (MITgcm.Superior) shows that physical gradients cause large variation in rates of both production (P) and respiration (R) between nearshore and offshore waters.  Accounting for this variability helps to bring the lake-wide carbon budget into balance (Bennington et al. 2012, JGR). In the model, fluxes of organic carbon from nearshore lead to elevated R:P ratios in the slope region, which could support the observed enhanced heterotrophic biomass on the slope (McKinley and Bennington, in prep). Lastly, in all the Great Lakes, I demonstrate that increasing atmospheric CO2 should lead to a reduction of pH by ~0.3 units by 2100, quantitatively the same as projections for “ocean acidification” in the global oceans. In the Great Lakes, the existing carbon cycle observational system is insufficient to track such changes (Phillips et al. 2015).

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