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Interactive Carbon Studies AK Water Office Overview Hypotheses Hydrology Site Qualification Sites Sample Collection Crew Rosters Personnel Training 2004 Summary 6/04 Log/Photos 8/04 Log/Photos 2003 Summary 6/03 Log/Photos 8/03 Log/Photos 2002 Summary 6/02 Log/Photos 8/02 Log/Photos Products/Biblio Related Links |
Project Hypotheses
Rob StrieglCarbon cycling and export by the Yukon RiverClimate change is expected to have considerable impact on the source, transformation, and export of inorganic and organic carbon transported by the Yukon River and exported to the Bering Sea. Carbon sources to the river include particulate carbonates (PIC) in suspended glacial melt-water sediments, dissolved inorganic carbon (CO2(g), H2CO3*, HCO3-, CO3-2) in precipitation runoff and ground water, and particulate and dissolved organic carbon (POC and DOC) in terrestrial runoff. Within-river transformations of C include carbonic acid weathering of PIC to DIC and metabolism of POC and DOC to DIC. The bioavailability organic carbon transported by the river varies depending on the plant material source and the extent of microbial transformation of organic C that has occurred in soils and wetlands prior to delivery to the river. Losses of C from the river include sedimentation of PIC, river discharge to the Bering Sea, and evasion of CO2 and CH4 to the atmosphere. The first phase of our study of C cycling and export by the Yukon River is to quantify these C biogeochemical interactions to account for C sources and sinks in the river and C export by the river under current climate conditions. As climate warms in the Yukon basin, we hypothesize rapid melting of permafrost in many areas, depletion of glacial sources of melt water, increased microbial processing of organic C in soils and wetlands as biologically active layers deepen, and release of large quantities of organic C currently frozen in permafrost to metabolism within the basin and to export from the basin. The second phase of our research focuses on quantification of these hypothesized changes. Incubation experiments provide bounds on rates of within-stream metabolism of DOC from source areas having different permafrost extent and vegetation types. Calculations of PIC transport and dissolution quantify reductions in these processes that will occur as glacial sources are depleted. Characterization of the chemical composition of DOC from various land cover sources provides insight to changes that may occur in the composition and bioreactivity of DOC exported to the Bering Sea. The net result is an improved understanding of current C cycling in the Yukon River basin and of changes that will occur as climate warming progresses in the basin. |
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