Northern rivers connect a land area of approximately 20.5 million km2 to the Arctic Ocean and surrounding seas. These rivers account for ~10% of global river discharge and transport massive quantities of dissolved and particulate materials that reflect watershed sources and impact biogeochemical cycling in the ocean. In this paper, multiyear data sets from a coordinated sampling program are used to characterize particulate organic carbon (POC) and particulate nitrogen (PN) export from the six largest rivers within the pan-Arctic watershed (Yenisey, Lena, Ob', Mackenzie, Yukon, Kolyma). Together, these rivers export an average of 3055 × 109 g of POC and 368 × 109 g of PN each year. Scaled up to the pan-Arctic watershed as a whole, fluvial export estimates increase to 5767 × 109 g and 695 × 109 g of POC and PN per year, respectively. POC export is substantially lower than dissolved organic carbon export by these rivers, whereas PN export is roughly equal to dissolved nitrogen export. Seasonal patterns in concentrations and source/composition indicators (C:N, δ13C, Δ14C, δ15N) are broadly similar among rivers, but distinct regional differences are also evident. For example, average radiocarbon ages of POC range from ~2000 (Ob') to ~5500 (Mackenzie) years before present. Rapid changes within the Arctic system as a consequence of global warming make it challenging to establish a contemporary baseline of fluvial export, but the results presented in this paper capture variability and quantify average conditions for nearly a decade at the beginning of the 21st century.
Bibliographical noteFunding Information:
We thank Yana Adreeva, Bart Blais, Tim Brabets, Ludmila Boeva, Charlie Couvillon, Elena Dunaeva, Martin Kelly, Ludmila Kosmenko, Dave Milburn, Anna Suslova, Mikhail Suslov, and Suzanne Thomas, for assistance with project implementation, including sample collection, sample analysis, and/or coordination efforts. We also thank CH2M HILL Polar Services for logistical support. This work was supported by the National Science Foundation through grants 0229302 and 0732985. Additional support was provided by the U.S. Geological Survey (Yukon River) and the Department of Indian and Northern Affairs (Mackenzie River). All of the data used in this paper are freely available at www.arcticgreatrivers.org/data.html.