The export and A ??14C-age of dissolved organic carbon (DOC) was determined for the Yehisey, 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. ??14C-DOC shows a clear relationship with hydrology. A small pool of DOC slightly depleted in ??14C is exported with base flow. The large pool exported with spring thaw is enriched in ??14C with respect to current-day atmospheric ??14C-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 export a large amount of young and presumably semilabile DOC to the Arctic Ocean. Copyright 2007 by the American Geophysical Union.
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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