Ninth International Conference on Permafrost ... - IARC Research

The Role of Lakes in Carbon Transfers from Permafrost to the Atmosphere: EightMile Lake, AlaskaJames O. Sickman, Guntram Von Kiparski, William VicarsDepartment of Environmental Sciences, University of California, Riverside, Riverside, CA 92521, USAEdward A.G. Schuur, Jason G. VogelDepartment of Botany, University of Florida, Gainesville, FL 32601-8526, USAIntroductionIn the permafrost-affected watersheds of the arctic andsubarctic, dissolved carbon losses can be considerable,accounting for over 37% of net ecosystem production (NEP)in some regions (Judd & Kling 2002). Therefore, dissolvedcarbon flux may be an important determinant of regionalcarbon balance in the arctic and subarctic, but more researchis needed to understand how these fluxes will respond towarming and whether downstream lacustrine systems canattenuate losses of terrestrial carbon.The main objectives of our study were to quantifyhydrologic losses of carbon along a gradient of permafrostthaw in the Eight Mile Lake watershed and assess the effectof in-lake processes on watershed carbon losses.Materials and MethodsField siteThe Eight Mile Lake Watershed (EMLW) is located nearHealy, Alaska, near Denali National Park. Elevation range inthe watershed ranges from 656 to 1057 m, and the drainagearea is 1108 hectares. The maximum depth and area of thelake are 3 m and 69 hectares. Within the catchment, plotstudies have been initiated across a gradient of permafrostthaw: severely thawed (Old Karst), moderately thawed (NewKarst), and not thawed. (Tussock)Field and laboratory measurementsDuring 2006, we measured concentrations and estimatedfluxes of dissolved organic carbon (DOC) and dissolvedinorganic carbon (DIC) at both plot (1000 ha) scales. Stream samples were collected every twodaysusing ISCO automated samplers during snowmelt (Mayand June) and manually every week during July throughSeptember (surface streams freeze in late September). Soilwater was sampled at multiple depths within the tundra activelayer using specialized lysimeters called Multisamplers(Martin et al. 2003). Inlet stage was measured in a culvertto a road that bisects the watershed and used to weight lakeinlet and outlet chemistry for computation of C fluxes to thelake. Annual runoff was estimated as the difference betweenwatershed precipitation and evaporation.DOC was measured by high-temperature catalyzed combustionon a Shimadzu TOC 5000. Dissolved CO 2(thedominant form of DIC in these low pH (