Carbon export and particulate trace metal cycling across the Western Arctic Ocean

Erin E Black1,2, Matthew A Charette3, Phoebe J Lam4, Robert F Anderson5, Lauren Elizabeth Kipp6, Yang Xiang4, Sebastian M Vivancos7, Stephanie Kienast1 and Ken Buesseler8, (1)Dalhousie University, Halifax, NS, Canada, (2)Lamont -Doherty Earth Observatory, Palisades, United States, (3)Woods Hole Oceanographic Institution, Marine Chemistry & Geochemistry, Woods Hole, MA, United States, (4)University of California Santa Cruz, Department of Ocean Sciences, Santa Cruz, CA, United States, (5)Lamont-Doherty Earth Obs, Palisades, NY, United States, (6)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (7)Columbia University, Department of Earth and Environmental Sciences, New York, NY, United States, (8)Woods Hole Oceanographic Institution, Department of Marine Chemistry & Geochemistry, Woods Hole, MA, United States
As a part of the 2015 U.S. GEOTRACES program’s efforts to examine basin-scale patterns in the Arctic Ocean, the components of three key, Thorium-based systems were measured. Thorium-234 (t½~24 d), Thorium-228 (t½~1.9 yr), and Thorium-230 (t½~75,380 yr) are naturally occurring radioisotopes whose disequilibrium with parents Uranium-238, Radium-228, and Uranium-234 can be exploited to quantify fluxes of carbon and other particulate constituents sinking out of the upper ocean. The concurrent sampling of these three isotope systems provides insight into the particulate cycling of these components over seasonal to sub-decadal timescales and throughout the entire water column.

Carbon flux estimates show contrasting patterns in export between the broad Arctic shelves and the oligotrophic central Arctic basin. Some of the longer-lived isotope data also indicate a difference in export between the Makarov and the deeper Canada Basins. These regional differences in the biological carbon pump will be explored further in the context of existing historical sediment trap data. In addition, the export fluxes of trace elements (e.g. iron, cobalt, and manganese) from these same regions will be presented. The (de-)coupling of these trace element systems with the carbon cycle in the Arctic will be examined along the shelf-basin continuum and from basin to basin within the Western Arctic Ocean to improve our understanding of the drivers of carbon and micronutrient export in this rapidly changing region.