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Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers
Yale School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA
University of Texas at Austin, Port Aransas, Texas, USA
Woods Hole Research Center, Falmouth, Massachusetts, USA
South Russian Regional Centre for Preparation and Implementation of International Projects, Rostov-on-Don, Russia
Yale School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA
Marine Biological Laboratory, Woods Hole, Massachusetts, USA
U.S. Geological Survey, Denver, Colorado, USA
U.S. Geological Survey, Boulder, Colorado, USA
South Russian Regional Centre for Preparation and Implementation of International Projects, Rostov-on-Don, Russia
The export and Δ14C-age of dissolved organic carbon (DOC) was determined for the Yenisey, Lena, Ob', Mackenzie, and Yukon rivers for 2004–2005. Concentrations of DOC elevate significantly with increasing discharge in these rivers, causing approximately 60% of the annual export to occur during a 2-month period following spring ice breakup. We present a total annual flux from the five rivers of ∼16 teragrams (Tg), and conservatively estimate that the total input of DOC to the Arctic Ocean is 25–36 Tg, which is ∼5–20% greater than previous fluxes. These fluxes are also ∼2.5× greater than temperate rivers with similar watershed sizes and water discharge. Δ14C-DOC shows a clear relationship with hydrology. A small pool of DOC slightly depleted in Δ14C is exported with base flow. The large pool exported with spring thaw is enriched in Δ14C with respect to current-day atmospheric Δ14C-CO2 values. A simple model predicts that ∼50% of DOC exported during the arctic spring thaw is 1–5 years old, ∼25% is 6–10 years in age, and 15% is 11–20 years old. The dominant spring melt period, a historically undersampled period, exports a large amount of young and presumably semilabile DOC to the Arctic Ocean.
Received 17 January 2007; accepted 6 July 2007; published 2 November 2007.
Citation: (2007), Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers, Global Biogeochem. Cycles, 21, GB4011, doi:10.1029/2007GB002934.
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