The fate of terrestrial dissolved organic matter in the Eurasian basin of the Arctic Ocean

Continental margins in the Eurasin Basin receive vast amounts of terrigenous dissolved organic carbon (tDOC) delivered from Arctic watersheds that store approximately 50% of global soil organic carbon mostly held in peat bogs and permafrost soils. Dissolved lignin phenols were analyzed in combination with optical parameters to gain a better understanding of decomposition pathways of tDOC in the Arctic Ocean and export of tDOC to surface and deep waters of the North Atlantic. Filtered waster samples and large-volume dissolved organic matter (DOM) extracts were collected during the Nansen and Admundsen Basin Observation System (NABOS) cruise along mooring locations in the Barents, Laptev and East-Siberian Seas in 2008. A large amount of river water was found near the Lomonossov Ridge and in the East Siberian Sea. Mineralization rates of tDOC exported from the shelves were determined with correlations of DOC-normalized yields of nine lignin phenols (TDLP₉-C) with river fractions calculated from a four-component water mass balance and accounting for freshwater input through precipitation. The calculated decay rate for tDOC leaving the shelf and supplied by the Siberian rivers during high discharge was 0.51±0.11 yr^-1 indicating the susceptibility of tDOC to mineralization. Acid/aldehyde ratios of vanillyl and syringyl lignin phenols showed that biomineralization was the dominant mechanism for the removal of tDOC. The quality of tDOC constituents lead to a dispersion of decay rates dependent on the residence time. Accounting for time-dependent decay rates of tDOC, the export of tDOC to surface and deep waters of the North Atlantic and its linkage to Arctic atmospheric circulations, specifically the Arctic Oscillation (AO) and the Arctic Dipole, is discussed.