Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal

Tank, Suzanne; Frey, Karen E.; Striegl, Robert G.; Raymond, Peter A.; Holmes, R. Max; McClelland, James W.; Peterson, Bruce J.

Abstract:

While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO₂, a substantial fraction of riverine bicarbonate (HCO₃^-) flux represents a CO₂ sink, as a result of weathering processes that sequester CO₂ as HCO₃^-. We explored landscape-level controls on DOC and HCO₃^- flux in subcatchments of the boreal, with a specific focus on the effect of permafrost on riverine dissolved C flux. To do this, we undertook a multivariate analysis that partitioned the variance attributable to known, key regulators of dissolved C flux (runoff, lithology, and vegetation) prior to examining the effect of permafrost, using riverine biogeochemistry data from a suite of subcatchments drawn from the Mackenzie, Yukon, East, and West Siberian regions of the circumboreal. Across the diverse catchments that we study, controls on HCO₃^- flux were near-universal: runoff and an increased carbonate rock contribution to weathering (assessed as riverwater Ca:Na) increased HCO₃^- yields, while increasing permafrost extent was associated with decreases in HCO₃^-. In contrast, permafrost had contrasting and region-specific effects on DOC yield, even after the variation caused by other key drivers of its flux had been accounted for. We used ionic ratios and SO₄ yields to calculate the potential range of CO₂ sequestered via weathering across these boreal subcatchments, and show that decreasing permafrost extent is associated with increases in weathering-mediated CO₂ fixation across broad spatial scales, an effect that could counterbalance some of the organic C mineralization that is predicted with declining permafrost.

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Article

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70039855

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Tank, Suzanne ; Frey, Karen E.; Striegl, Robert G.; Raymond, Peter A.; Holmes, R. Max; McClelland, James W.; Peterson, Bruce J.

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Branch of Regional Research Central Region

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English

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Global Biogeochemical Cycles

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15 p.; GB0E02

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American Geophysical Union

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Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal; 2012; Article; Journal; Global Biogeochemical Cycles; Tank, Suzanne ; Frey, Karen E.; Striegl, Robert G.; Raymond, Peter A.; Holmes, R. Max; McClelland, James W.; Peterson, Bruce J.