Search

Biogeochemical cycling in the extensive shelf seas and in the interior basins of the semi-enclosed Arctic Ocean are strongly influenced by land-ocean transport of carbon and other elements. The Arctic carbon cycle system is also inherently connected with the climate, and thus vulnerable to environmental and climate changes. Sediments of the Arctic Ocean are an active and integral part in Arctic biogeochemical cycling, and provide the opportunity to study present and historical input and fate of organic matter (e.g., through permafrost thawing). To compare differences between the Arctic regions and to study Arctic biogeochemical budgets, comprehensive sedimentary records are required. To this end, the Circum-Arctic Sediment CArbon DatabasE (CASCADE) was established to curate data primarily on concentrations of organic carbon (OC) and OC isotopes (d13C, Δ14C), yet also on total N (TN) as well as of terrigenous biomarkers and other sediment geochemical and physical properties drawn both from the published literature and from earlier unpublished records through an extensive international community collaboration. This paper describes the establishment, structure and current status of CASCADE. This first public version includes OC concentrations in surface sediments at 4244 oceanographic stations including 2317 with TN concentrations, 1555 with d13C-OC values, 268 with Δ14C-OC values and 653 records with quantified terrigenous biomarkers (high molecular weight n-alkanes, n-alkanoic acids and lignin phenols) distributed over the shelves and the central basins of the Arctic Ocean. CASCADE also includes data from 326 sediment cores, retrieved by shallow box- or multi-coring and deep gravity/piston coring, as well as sea-bottom drilling. The comprehensive dataset reveals several large-scale features, including clear differences in both OC content and isotope-based diagnostics of OC sources between the shelf sea recipients. This indicates, for instance, the release of strongly pre-aged terrigenous OC to the East Siberian Arctic shelf and younger terrigenous OC to the Kara Sea and thus provides clues about land-ocean transport of material released by thawing permafrost. CASCADE enables synoptic analysis of OC in Arctic Ocean sediments and facilitates a wide array of future empirical and modelling studies of the Arctic carbon cycle. CASCADE is openly and freely available online (https://doi.org/10.17043/cascade; Martens et al., 2020b), is provided in various machine-readable data formats (data tables, GIS shapefile, GIS raster), and also provides ways for contributing data for future CASCADE versions. CASCADE will be continuously updated with newly published and contributed data over the foreseeable future as part of the database management of the Bolin Centre for Climate Research at Stockholm University. [ABSTRACT FROM AUTHOR]

We report, for the first time, the solemyid Acharax svalbardensis sp. nov., from deep-sea methane seep sites on the western Svalbard margin, 79°N. This species is rather small and so far the northernmost representative of its genus. It is identified based on the following combination of diagnostic characters: umbo 27–30% valve length from posterior margin; H/L ratio ∼0.35; broadly rounded to truncated anterior margin; 15 moderately developed, flat double ribs with middle ribs about as strong as posterior ribs. The shells from Acharax svalbardensis sp. nov. were found in sediment cores from two pockmarks at Vestnesa Ridge at ∼1200 m water depth in the Fram Strait off NW Spitsbergen, Svalbard archipelago. Previously, the vesicomyid bivalves Archivesica arctica and Isorropodon nyeggaensis have been documented from the same pockmarks. Here, we describe the new solemyid species and report its stratigraphical occurrence and co-occurrence with the previously described methane seep-associated vesicomyids. All findings of the vesicomyids and the new solemyid species are restricted to the time interval ∼19,000–15,600 cal. years BP, correlating with Heinrich Stadial HS1. This period was characterized by cold surface conditions and extensive ice rafting from sea ice and icebergs in the North Atlantic and Arctic region. Inflow of a warm subsurface current of Atlantic water below the melt water layer led to higher bottom water temperatures at the Svalbard margin than at present. This increase in bottom water temperature probably allowed several methane seep-associated bivalve species to settle for a short period of time, namely the vesicomyids A. arctica and I. nyeggaensis and the new species of the solemyid bivalve genus Acharax described here. [ABSTRACT FROM AUTHOR]