Abstract
Abstract. Subsurface hydrological flow pathways and advection rates through the landscape affect the quantity and timing of hydrological transport of dissolved carbon. This study investigates hydrological carbon transport through the subsurface to streams and how it is affected by the distribution of subsurface hydrological pathways and travel times through the landscape. We develop a consistent mechanistic, pathway- and travel time-based modeling approach for release and transport of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The model implications are tested against observations in the subarctic Abiskojokken catchment in northernmost Sweden (68°21' N, 18°49' E) as a field case example of a discontinuous permafrost region. The results show: (a) For DOC, both concentration and load are essentially flow-independent because their dynamics are instead dominated by the annual renewal and depletion. Specifically, the flow independence is the result of the small characteristic DOC respiration-dissolution time scale, in the range of 1 yr, relative to the average travel time of water through the subsurface to the stream. (b) For DIC, the load is highly flow-dependent due to the large characteristic weathering-dissolution time, much larger than 1 yr, relative to the average subsurface water travel time to the stream. This rate relation keeps the DIC concentration essentially flow-independent, and thereby less fluctuating in time than the DIC load.
Highlights
The hydrological transport of carbon has recently begun to be included in global carbon (C) budgets (Cole et al, 2007)
The aim of the calculation examples is to demonstrate what the flow-independent dynamics of normalized concentration c and mass flux s from Eqs. (3)–(5) may look like under various conditions of relevance for dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) release and transport
This annual periodicity implies that the characteristic DOC release time 1/k should be on the order of 1 yr or smaller
Summary
The hydrological transport of carbon has recently begun to be included in global carbon (C) budgets (Cole et al, 2007). Due to ongoing climatic warming, these systems can evolve such that they no longer serve as clear net carbon sinks and can potentially become large net carbon sources (Kling et al, 1991; ACIA, 2005; Fung et al, 2005; Schuur et al, 2008). In this important context, our knowledge is limited on how sources release carbon and how DOC and DIC are further transported from the ground and into streams and other aquatic ecosystems in such high-latitude terrestrial systems
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