230Th and 231Pa: Tracers for Deep Water Circulation and Particle Fluxes in the Arctic Ocean

Ole Valk1, Michiel Rutgers van der Loeff1, Viena Puigcorbe Lacueva2, Ronja Paffrath3 and Sandra Gdaniec4, (1)Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Marine Geochemistry, Bremerhaven, Germany, (2)Universitat Autònoma de Barcelona, , Institut de Ciència I Tecnologia Ambientals & Department of Physics, Barcelona, Spain, (3)ICBM, Max Planck Research Group for Marine Isotope Geochemistry Institute for Chemistry and Biology of the Marine Environment University of Oldenburg, Oldenburg, Germany, (4)SMNH, Swedish Museum of Natural History, Department of Geosciences, Stockholm, Sweden, Stockholm, Sweden
Abstract:
230Th and 231Pa data from the central Arctic Ocean is very limited. 230Th and 231Pa are produced at a constant rate in the water column by radioactive decay of Uranium isotopes (234U and 235U respectively) (e.g. Anderson et al., 1983). They are both particle reactive and are scavenged on settling particles. As 230Th is more particle reactive than 231Pa, their distribution in the water column and activity ratio give us information about particle fluxes and circulation patterns and –intensities (Henderson et al., 1999; Scholten et al., 2001).

The Arctic Ocean is an almost landlocked ocean with limited connections to the Atlantic and Pacific and a high input of river water. About 10 % of the global river run-off is delivered to the Arctic Ocean. Due to climate change the Arctic Ocean will undergo dramatic changes in sea ice cover and supply of fresh water, while increasing coastal erosion will cause an increased input of terrestrial material (Peterson et al., 2002). This will influence the biogeochemical cycling and transport of carbon, nutrients and trace elements (IPCC, 2007). We expect that the distribution of 230Th and 231Pa will reflect changes in particle fluxes and shelf-basin exchange (Roy-Barman, 2009). We will present the first results of 230Th and 231Pa, in combination with on board measured particulate 234Th, collected during the 2015 Polarstern section (GEOTRACES section GN04 2015) through the Nansen, Amundsen, and Makarov Basins.

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Scholten, J. C., et al. (2001). DSR II 48: 2383-2408.

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