RESEARCH: Sargasso Sea

Time-series measurements of bulk DON δ15N were used to confirm that NO3- is the dominant nitrogen source fueling export production throughout the year in the Sargasso Sea. Additionally, measurements of the total nitrogen flux in atmospheric deposition has a δ15N similar to that of N2 fixation. Consequently, the source of the low-δ15N NO3- in the upper thermocline of the North Atlantic could result from inputs from both N2 fixation and atmopsheric deposition.

Publications

  • Marconi, D., D. Sigman, K. Casciotti, E. Campbell, M. Weigand, S. Fawcett, A. Knapp, P. Rafter, B. Ward, and G. Haug, Tropical dominance of N2 fixation in the North Atlantic Ocean, 2017, Global Biogeochemical Cycles, 31, doi:10.1002/2016GB005613

  • Letscher, R.T., D.A. Hansell, C.A. Carlson, R. Lumpkin, and A.N. Knapp, 2013, *Dissolved organic nitrogen in the global surface ocean: Distribution and fate, Global Biogeochem. Cycles, 27, doi/10.1029/2012GB004449/

    • *See associated Nature "News and Views" article by Voss and Heitanen

  • Knapp, A.N., D.M. Sigman, A.B. Kustka, S.A. Sanudo-Wilhelmy, and D.G. Capone, 2012, The distinct nitrogen isotopic compositions of low and high molecular weight DON, Marine Chemistry, 136-137, 24-33, doi:10.1016/j.marchem.2012.05.001

  • Knapp, A.N., D.M. Sigman, F. Lipschultz, A.B. Kustka, and D.G. Capone, 2011, Interbasin isotopic correspondence between upper-ocean bulk DON and subsurface nitrate and its implications for marine nitrogen cycling, Global Biogeochemical Cycles, 25, GB4004, doi:10.1029/2010GB003878

  • Knapp, A.N., M.G. Hastings, D.M. Sigman, F. Lipschultz and J.N. Galloway, 2010, The flux and isotopic composition of reduced and total nitrogen in Bermuda rain, Marine Chemistry, 120, 83-89, doi:10.1016/j.marchem.2008.08.007 (Published online in final form in 2008)

  • Sigman, D.M., P.J. DiFiore, M.P. Hain, C. Deutsch, Y. Wang, D.M. Karl, A.N. Knapp, M.F. Lehmann, and S. Pantoja, 2009, The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen. Deep-Sea Res. I, 56, 1419-1439, doi:10.1016/j.dsr.2009.04.007

  • Knapp, A.N., P.J. DiFiore, C. Deutsch, D.M. Sigman, and F. Lipschultz, 2008, Nitrate isotopic composition between Bermuda and Puerto Rico Implications for N2 fixation in the Atlantic Ocean, Global Biogeochem. Cycles, 22, GB3014.

  • Knapp, A.N., D.M. Sigman, and F. Lipschultz, 2005, N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic Time-series Study site, Global Biogeochem. Cycles, 19, GB1018, doi:10.1029/2004GB002320

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