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

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

While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO 2 , a substantial fraction of riverine bicarbonate (HCO 3 - ) flux represents a CO 2 sink, as a result of weathering processes that sequester CO 2 as HCO 3 - . We explored landscape-level controls on DOC and HCO 3 - 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 HCO 3 - flux were near-universal: runoff and an increased carbonate rock contribution to weathering (assessed as riverwater Ca:Na) increased HCO 3 - yields, while increasing permafrost extent was associated with decreases in HCO 3 - . 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 SO 4 yields to calculate the potential range of CO 2 sequestered via weathering across these boreal subcatchments, and show that decreasing permafrost extent is associated with increases in weathering-mediated CO 2 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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Suzanne Tank, Karen E. Frey, Robert G. Striegl, Peter A. Raymond, R. Max Holmes, James W. McClelland, Bruce J. Peterson. 2012-08-21. Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal. https://doi.org/10.1029/2012gb004299

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