Carbon fluxes from large water bodies may be important to understanding regional and continental carbon budgets. The Laurentian Great Lakes, with a surface area that comprises 3% of the continental United States may play an important role in the continental carbon budget, particularly in the upper Mid West, a region of focus by the North American Carbon Program (NACP). We examine mechanisms of carbon fluxes from Lake Superior at small and large spatial and temporal scales using available data. In the western arm, we consider the relationship between temperature, biological activity and pCO2 at daily to monthly time scales during the summer of 2001. We find that springtime pCO2 is determined predominantly by temperature, but after the Lake warms and stratifies, biological activity can draw down CO2 and rapidly decrease near-surface pCO2. The magnitude of the lake-wide flux is considered using a reanalysis of biannual lake-wide surveys from the USEPA and is coupled with an assessment of our current understanding of terrestrial carbon inputs. We link our analysis to a coupled physicalbiogeochemical model of the Lake to improve our understanding of the lake carbon budget, its spatial and temporal variability, and to quantitatively improve the carbon budget.

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