Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion

• Published in: Biogeosciences
• Main Authors: I. P. Semiletov, I. I. Pipko, N. E. Shakhova, O. V. Dudarev, S. P. Pugach, A. N. Charkin, C. P. McRoy, D. Kosmach, Ö. Gustafsson
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2011
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Arctic Ocean; Laptev Sea; Yakutsk; laptev; lena river
• Online Access: https://doi.org/10.5194/bg-8-2407-2011; https://doaj.org/article/f7d98d0dc26d41fa82e6e438775a39f8

The Lena River integrates biogeochemical signals from its vast drainage basin, and the integrated signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon (OC) into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered to be quasi-steady-state processes. An increase in Lena discharge exerts opposite effects on total organic (TOC) and total inorganic (TCO 2 ) carbon: TOC concentration increases, while TCO 2 concentration decreases. Significant inter-annual variability in mean values of TCO 2 , TOC, and their sum (total carbon, TC) has been found. This variability is determined by changes in land hydrology which cause differences in the Lena River discharge. There is a negative correlation in the Lena River between TC in September and its mean discharge in August; a time shift of about one month is required for water to travel from Yakutsk to the Laptev Sea. Total carbon entering the sea with the Lena discharge is estimated to be almost 10 Tg C yr −1 . The annual Lena River discharge of particulate organic carbon (POC) can be as high as 0.38 Tg (moderate to high estimate). If we instead accept Lisytsin's (1994) statement that 85–95 % of total particulate matter (PM) (and POC) precipitates on the marginal "filter", then only about 0.03–0.04 Tg of Lena River POC reaches the Laptev Sea. The Lena's POC export would then be two orders of magnitude less than the annual input of eroded terrestrial carbon onto the shelf of the Laptev and East Siberian seas, which is estimated to be about 4 Tg. Observations support the hypothesis of a dominant role for coastal erosion (Semiletov, 1999a, b) in East Siberian Arctic Shelf (ESAS) sedimentation and the dynamics of the carbon/carbonate system. The Lena River is characterized by relatively high concentrations of the primary greenhouse gases, dissolved carbon dioxide (CO 2 ) and methane (CH 4 ). During all seasons the river is supersaturated in CO 2 compared to the atmosphere, by up to 1.5–2 fold in ...