Geochemical tracers of Arctic river waters

The research presented in this dissertation examines the utility of naturally occurring geochemical signals for tracing the fluvial component of Arctic Ocean circulation. The dissertation comprises separate manuscripts that have been or will be submitted for publication in peer-reviewed journals.;An extensive survey of dissolved organic carbon (DOC) in the Arctic Ocean was achieved by means of a high-resolution, in situ UV fluorometer deployed on a nuclear submarine. Based on a strong linear correlation observed between fluorescence (320 nm excitation, 420 nm emission) and organic carbon concentrations determined directly by high-temperature combustion, a continuous record of DOC was produced at a keel depth of 58 m along a 2900-km transect north of the Beaufort, Chukchi, East Siberian and Laptev seas. The DOC record, combined with other physical and chemical measurements, identifies areas where river waters cross the shelves and enter the circulation of the interior Arctic Ocean. Fluvial sources were found to account for 12--56% of the total DOC in parts of the upper Makarov and Amundsen basins.;Distributions of temperature, salinity and barium are presented for the upper Laptev Sea and adjacent areas of the Nansen, Amundsen and Makarov basins during the summer in 1993, 1995 and 1996. Preliminary results of q-mode factor analysis captured the Atlantic and fluvial end-members of a mixing model proposed for the Laptev Sea. Distributions of fluvial discharge inferred from the tracer measurements are consistent with local winds and suggest two principal pathways by which river waters can enter the interior Arctic Ocean from the Laptev Sea. When southerly to southeasterly wind conditions prevail, river waters are transported northwards beyond the shelf break and over the slope and adjacent basin areas. These waters can then enter the interior Arctic Ocean via upper layer flow aligned roughly along the Lomonosov Ridge. Under other wind conditions, river waters are steered primarily along the inner Laptev shelf and into the East Siberian Sea as part of the predominantly eastward coastal current system. These waters then appear to cross the shelf and enter the interior Arctic Ocean via upper layer flow aligned roughly along the Mendeleyev Ridge.