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ArticleStrong margin influence on the Arctic Ocean Barium Cycle revealed by pan‐Arctic synthesis(American Geophysical Union, 2022-03-22) Whitmore, Laura M. ; Shiller, Alan M. ; Horner, Tristan J. ; Xiang, Yang ; Auro, Maureen E. ; Bauch, Dorothea ; Dehairs, Frank ; Lam, Phoebe J. ; Li, Jingxuan ; Maldonado, Maria T. ; Mears, Chantal ; Newton, Robert ; Pasqualini, Angelica ; Planquette, Helene ; Rember, Robert ; Thomas, HelmuthEarly studies revealed relationships between barium (Ba), particulate organic carbon and silicate, suggesting applications for Ba as a paleoproductivity tracer and as a tracer of modern ocean circulation. But, what controls the distribution of barium (Ba) in the oceans? Here, we investigated the Arctic Ocean Ba cycle through a one-of-a-kind data set containing dissolved (dBa), particulate (pBa), and stable isotope Ba ratio (δ138Ba) data from four Arctic GEOTRACES expeditions conducted in 2015. We hypothesized that margins would be a substantial source of Ba to the Arctic Ocean water column. The dBa, pBa, and δ138Ba distributions all suggest significant modification of inflowing Pacific seawater over the shelves, and the dBa mass balance implies that ∼50% of the dBa inventory (upper 500 m of the Arctic water column) was supplied by nonconservative inputs. Calculated areal dBa fluxes are up to 10 μmol m−2 day−1 on the margin, which is comparable to fluxes described in other regions. Applying this approach to dBa data from the 1994 Arctic Ocean Survey yields similar results. The Canadian Arctic Archipelago did not appear to have a similar margin source; rather, the dBa distribution in this section is consistent with mixing of Arctic Ocean-derived waters and Baffin Bay-derived waters. Although we lack enough information to identify the specifics of the shelf sediment Ba source, we suspect that a sedimentary remineralization and terrigenous sources (e.g., submarine groundwater discharge or fluvial particles) are contributors.
ArticleA comprehensive global oceanic dataset of helium isotope and tritium measurements.(Copernicus Publications, 2019-04-05) Jenkins, William J. ; Doney, Scott C. ; Fendrock, Michaela ; Fine, Rana A. ; Gamo, Toshitaka ; Jean-Baptiste, Philippe ; Key, Robert M. ; Klein, Birgit ; Lupton, John E. ; Newton, Robert ; Rhein, Monika ; Roether, Wolfgang ; Sano, Yuji ; Schlitzer, Reiner ; Schlosser, Peter ; Swift, James H.Tritium and helium isotope data provide key information on ocean circulation, ventilation, and mixing, as well as the rates of biogeochemical processes and deep-ocean hydrothermal processes. We present here global oceanic datasets of tritium and helium isotope measurements made by numerous researchers and laboratories over a period exceeding 60 years. The dataset's DOI is https://doi.org/10.25921/c1sn-9631, and the data are available at https://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March 2019) or alternately http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/ (last access: 13 March 2019) and includes approximately 60 000 valid tritium measurements, 63 000 valid helium isotope determinations, 57 000 dissolved helium concentrations, and 34 000 dissolved neon concentrations. Some quality control has been applied in that questionable data have been flagged and clearly compromised data excluded entirely. Appropriate metadata have been included, including geographic location, date, and sample depth. When available, we include water temperature, salinity, and dissolved oxygen. Data quality flags and data originator information (including methodology) are also included. This paper provides an introduction to the dataset along with some discussion of its broader qualities and graphics.
ArticleThe transpolar drift as a source of riverine and shelf-derived trace elements to the central Arctic Ocean(American Geophysical Union, 2020-04-08) Charette, Matthew A. ; Kipp, Lauren ; Jensen, Laramie T. ; Dabrowski, Jessica S. ; Whitmore, Laura M. ; Fitzsimmons, Jessica N. ; Williford, Tatiana ; Ulfsbo, Adam ; Jones, Elizabeth M. ; Bundy, Randelle M. ; Vivancos, Sebastian M. ; Pahnke, Katharina ; John, Seth G. ; Xiang, Yang ; Hatta, Mariko ; Petrova, Mariia V. ; Heimbürger, Lars-Eric ; Bauch, Dorothea ; Newton, Robert ; Pasqualini, Angelica ; Agather, Alison ; Amon, Rainer M. W. ; Anderson, Robert F. ; Andersson, Per S. ; Benner, Ronald ; Bowman, Katlin ; Edwards, R. Lawrence ; Gdaniec, Sandra ; Gerringa, Loes J. A. ; González, Aridane G. ; Granskog, Mats A. ; Haley, Brian ; Hammerschmidt, Chad R. ; Hansell, Dennis A. ; Henderson, Paul B. ; Kadko, David C. ; Kaiser, Karl ; Laan, Patrick ; Lam, Phoebe J. ; Lamborg, Carl H. ; Levier, Martin ; Li, Xianglei ; Margolin, Andrew R. ; Measures, Christopher I. ; Middag, Rob ; Millero, Frank J. ; Moore, Willard S. ; Paffrath, Ronja ; Planquette, Helene ; Rabe, Benjamin ; Reader, Heather ; Rember, Robert ; Rijkenberg, Micha J. A. ; Roy-Barman, Matthieu ; van der Loeff, Michiel Rutgers ; Saito, Mak A. ; Schauer, Ursula ; Schlosser, Peter ; Sherrell, Robert M. ; Shiller, Alan M. ; Slagter, Hans ; Sonke, Jeroen E. ; Stedmon, Colin ; Woosley, Ryan J. ; Valk, Ole ; van Ooijen, Jan ; Zhang, RuifengA major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25–50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s−1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.