Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 5 2008 10.5194/bg-5-1437-2008 http://www.biogeosciences.net/5/1437/2008/ http://www.biogeosciences.net/5/1437/2008/bg-5-1437-2008.html http://www.biogeosciences.net/5/1437/2008/bg-5-1437-2008.pdf 1437 1455 2008-10-27 Importance of dissolved organic nitrogen in the north Atlantic Ocean in sustaining primary production: a 3-D modelling approach G. Charria guillaume.charria@legos.obs-mip.fr I. Dadou J. Llido M. Drévillon V. Garçon Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR5566/CNRS/UPS, Toulouse, France National Oceanography Centre, Southampton, UK Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht, The Netherlands European Centre for Research and Advanced Training in Scientific Computation, Toulouse, France An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical north Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN m−2 yr−1 over the domain (13–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN s−1) confirms the estimation (17.9 kmolN s−1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN m−2 yr−1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the north Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen. Aiken, J. and Bale, A. J.: An introduction to the Atlantic Meridional Transect (AMT) programme, Prog. Oceanogr., 45, 251–256, 2000. Ammerman, J. W., Hood, R. R., Case, D. A., and Cotner, J. B.: Phosphorus deficiency in the Atlantic: An emerging paradigm in oceanography, EOS, 84, 165–170, 2003. Antoine, D. and Morel, A.: Ocean Primary Production, 2: Estimation at global scale from satellite (Coastal Zone Color Scanner) chlorophyll, Global Biogeochem. Cy., 10, 57–69, 1996. Barnier, B., Miranda, A., Crosnier, L., Molines, J.-M., Tréguier A.-M., and Jouzeau, A.: Rapport scientifique et technique 1999, N°CLIPPER-R3-2000, LPO, Brest, 2000. Barnier, B., Madec, G., Penduff, T., Molines, J.-M., Tréguier, A.-M., Le Sommer, J., Beckmann, A., Biastoch, A., Böning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theetten, S., Maltrud, M., McClean, J., and De~Cuevas, B.: Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution, Ocean Dynam., 56, 543–567, 2006. Behrenfeld, M. J., and Falkowski, P.: Photosynthetic rates derived from satellite-based chlorophyll concentration, Limnol. Oceanogr., 42, 1–20, 1997. Berline, L., Brankart, J. M., Brasseur, P., Ourmières, Y., and Verron, J.: Improving the physics of a coupled physical-biogeochemical model of the North Atlantic through data assimilation: Impact on the ecosystem, J. Marine Syst., 64(1–4), 153–172, 2007. Blanke, B. and Delecluse, P.: Variability of the tropical Atlantic ocean simulated by a general circulation model with two different mixed-layer physics, J. Phys. Oceanogr., 23, 1363–1388, 1993. Carr, M. E., Friedrichs, M. A. M., Schmeltz, M., et al.: A comparison of global estimates of marine primary production from ocean color, Deep-Sea Res. Pt II, 53(5–7), 741–770, 2006. Carlson, C. A. and Ducklow, H. W.: Dissolved organic carbon in the upper ocean of the central equatorial Pacific Ocean, 1992: daily and fine-scale vertical variations, Deep-Sea Res. Pt II, 42(2–3), 639–656, 1995. Charria, G.: Influence of Rossby waves on the biogeochemical system in the North Atlantic Ocean: Use of ocean colour remotely sensed data and of a coupled physical/biogeochemical model, PhD Thesis, University Paul Sabatier, Toulouse, France, 339~pp., 2005. Christian, J. R.: Biogeochemical cycling in the oligotrophic ocean: Redfield and non-Redfield models, Limmol. Oceanogr., 50(2), 646–657, 2005. Conkright, M., O'Brien, T., Levitus, S., Boyer, T. P., Antonov, J., and Stephens, C.: World Ocean Atlas 1998, NOAA Atlas NESDIS 36, US Government Printing Office, Washington, D. C., 245~pp., 1998. Dadou, I., Evans, G., and Garçon, V.: Using JGOFS in situ and ocean color data to compare biogeochemical models and estimate their parameters in the subtropical North Atlantic Ocean, J. Mar. Res., 62, 565–594, 2004. Drillet, Y., Bourdalle-Badie, R., Siefridt, L., and Le~Provost, C.: Meddies in the Mercator North Atlantic and Mediterranean sea eddy resolving model, J. Geophys. Res., 110, C03016, doi:10.1029/2003JC002170, 2005. Duce, R. A., LaRoche, J., Altieri, K., Arrigo, K. R., Baker, A. R., Capone, D. G., Cornell, S., Dentener, F., Galloway, J., Ganeshram, R. S., Geider, R. J., Jickells, T., Kuypers, M. M., Langlois, R., Liss, P. S., Liu, S. M., Middelburg, J. J., Moore, C. M., Nickovic, S., Oschlies, A., Pedersen, T., Prospero, J., Schlitzer, R., Seitzinger, S., Sorensen, L. L., Uematsu, M., Ulloa, O., Voss, M., Ward, B., and Zamora, L.: Impacts of Atmospheric Anthropogenic Nitrogen on the Open Ocean, Science, 320, 893–897, 2008. Ducklow, H. W.: Biogeochemical Provinces: Towards a JGOFS Synthesis, in: Ocean Biogeochemistry, edited by: Fasham, M. J. R., Springer, 3–17, 2003. Emerson, S., Quay, P., Karl, D., Winn, C., Tupas, L., and Landry, M.: Experimental determination of the organic carbon flux from open-ocean surface waters, Nature, 389(6654), 951–954, 1997. Estubier, A. and Lévy, M.: Quel schéma numérique pour le transport d'organismes biologiques par la circulation océanique? Note Technique du Pôle de modélisation, Institut Pierre-Simon Laplace (IPSL), 81~pp., 2000. Etienne, H. and Benkiran, M.: Multivariate assimilation in MERCATOR project: New statistical parameters from forecast error estimation, J. Marine Syst., 65, 430–449, 2007. Gruber, N. and Sarmiento, J. L.: Global patterns of marine nitrogen fixation and denitrification, Global Biogeochem. Cy., 11(2), 235–266, 1997. Gunson, J., Oschlies, A., and Garçon, V.: Sensitivity of ecosystem parameters to simulated satellite ocean colour data using a coupled physical-biological model of the North Atlantic, J. Mar. Res., 57, 613–639, 1999. Hansell, D. A., Ducklow, H. W., Macdonald, A. M., and Baringer, M. O.: Metabolic poise in the North Atlantic Ocean diagnosed from organic matter transports, Limnol. Oceanogr., 49(4), 1084–1094, 2004. Huret, M., Dadou, I., Dumas, F., Lazure, P., and Garçon, V.: Coupling physical and biogeochemical processes in the Río de la Plata plume, Cont. Shelf Res., 25(5–6), 629–653, 2005. Kähler, P. and Koeve, W.: Marine dissolved organic matter: can its C:N ratio explain carbon overconsumption?, Deep-Sea Res. Pt I, 48, 49–62, 2001. Kirchman, D. L., Lancelot, C., Fasham, M., Legendre, L., Radach, G., and Scott, M.: Dissolved organic matter in biogeochemical models in the ocean, in: Towards a model of ocean biogeochemical processes, Springer Verlag, Berlin, 209–225, 1993. Knapp, A. N., Sigman, D. M., and Lipschultz, F.: N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic Time-series Study site, Global Biogeochem. Cy., 19, GB1018, doi:10.1029/2004GB002320, 2005. Lipschultz, F., Bates, N., Carlson, C., and Hansell, D.: New production in the Sargasso Sea: History and current status, Global Biogeochem. Cy., 16, 1–16, 2002. Lomas, M. W. and Bates, N. R.: Potential controls on interannual partitioning of organic carbon during the winter/spring phytoplankton bloom at the Bermuda Atlantic Time-series (BATS) site, Deep-Sea Res. Pt I, 51, 1619–1636, 2004. Longhurst, A. R., Sathyendranath, S., Platt, T., and Caverhill, C.: An estimate of global primary production in the ocean from satellite radiometer data, J. Plankton Res., 17, 1245–1271, 1995. Longhurst, A. R.: Ecological Geography of the Sea, Academic Press, 542~pp., 1998. McClain, C. R., Signorini, S. R., and Christian, J. R.: Subtropical gyre variability observed by ocean-color satellites, Deep-Sea Res. Pt II, 51, 281–301, 2004. McGillicuddy, D. J. and Robinson, A. R.: Eddy-induced nutrient supply and new production in the Sargasso Sea, Deep-Sea Res. Pt I, 44(8), 1427–1450, 1997. Madec, G., Delecluse, P., Imbard, M., and Levy, C.: OPA~8.1 Ocean General Circulation Model reference manual, Note Technique du Pôle de modélisation, Institut Pierre-Simon Laplace (IPSL), France, 91~pp., 1999. Mahaffey, C., Williams, R. G., Wolff, G. A., and Anderson, W.: Physical supply of nitrogen to phytoplankton in the Atlantic Ocean, Global Biogeochem. Cy., 18, GB1034, doi:10.1029/2003GB002129, 2004. Mélin, F : Potentiel de la télédétection pour l'analyse des propriétés optiques du système océan-atmosphère et application à l'estimation de la photosynthèse phytoplanctonique, PhD~Thesis, University Paul Sabatier, Toulouse, 514~pp., 2003. Morel, A., Antoine, D., Babin, M., and Dandonneau, Y.: Measured and modeled primary production in the northeast Atlantic (EUMELI JGOFS program): The impact of natural variations in photosynthetic parameters on model predictive skill, Deep-Sea Res. Pt I, 43(8), 1273–1304, 1996. O'Reilly, J. E., Maritorena, S., Siegel, D. A., et al.: Ocean Color Chlorophyll $a$ Algorithms for SeaWiFS, OC2, and OC4: Version~4, SeaWiFS Postlaunch Calibration and Validation Analyses, Part~3, NASA Technical Memorandum~206892, 11, 9–23, 2000. Oschlies, A.: Can eddies make ocean deserts bloom?, Global Biogeochem. Cy., 16(4), 1106, doi:10.1029/2001GB001830, 2002. Oschlies, A. and Garçon, V.: An eddy-permitting coupled physical-biological model of the North Atlantic. 1. Sensitivity to advection numerics and mixed layer physics, Global Biogeochem. Cy., 13(1), 135–160, 1999. Palter, J. B., Lozier, M. S., and Barber, R. T.: The effect of advection on the nutrient reservoir in the North Atlantic subtropical gyre, Nature, 437, 687–692, 2005. Pujo-Pay, M. and Raimbault, P.: Observations chimiques et biomasse dans l'océan Atlantique tropical Nord, campagnes EUMELI, Résultats des measures, Rapport Centre Océanologique de Marseille, France, 65~pp., 1994. Pujo-Pay, M : L'azote et le phosphore en milieu marin, importance des formes organiques en milieu océanique du large, PhD Thesis, Université de la Méditerranée, Marseille, France, 164~pp., 1995. Reynaud, T., Legrand, P., Mercier, H., and Barnier, B.: A new analysis of hydrographic data in the Atlantic and its application to an inverse modelling study, International WOCE Newsletters, 32, 29–31, 1998. Reynolds, R. W. and Smith, T.: Improved global sea surface temperature analysis using optimum interpolation, J. Climate, 7, 929–948, 1994. Roussenov, V., Williams, R. G., Mahaffey, C., and Wolff, G. A.: Does the transport of dissolved organic nutrients affect production in the Atlantic Ocean?, Global Biogeochem. Cy., 20, GB3002, doi:10.1029/2005GB002510, 2006. Sakshaug, E., Andresen, K., and Kiefer, D.: A steady state description of growth and light absorption in the marine planktonic diatom Skeleronema costatum, Limnol. Oceanogr., 34(1), 198–205, 1989. Salihoglu, B., Garçon, V., Oschlies, A., and Lomas, M. W.: Influence of nutrient utilization and remineralization stoichiometry on phytoplankton species and carbon export: a modeling study at BATS, Deep-Sea Res. Pt I, 55, 73–107, 2008. Sarmiento, J. L., Slater, R. D., Fasham, M. J. R., Ducklow, H. W., Toggweiler, J. R., and Evans, G. T.: A Seasonal Three-Dimensional Ecosystem Model of Nitrogen Cycling in the North Atlantic Euphotic Zone, Global Biogeochem. Cy., 7(2), 417–450, 1993. Siegel, D. A., McGillicuddy Jr., D. J. , and Fields, E. A.: Mesoscale eddies, satellite altimetry, and new production in the Sargasso Sea, J. Geophys. Res., 104(C6), 13 359–13 379, 1999. Steinberg, D. K., Carlson, C. A., Bates, N. R., Johnson, R. J., Michaels, A. F., and Knap, A. H.: Overview of the US JGOFS Bermuda Atlantic Time-series Study (BATS): a decade-scale look at ocean biology and biogeochemistry, Deep-Sea Res. Pt II, 48, 1405–1447, 2001. Taylor, K. E.: Summarizing multiple aspects of model performance in a single diagram, J. Geophys. Res., 106(D7), 7183–7192, 2001. Tréguier, A. M., Barnier, B., de~Miranda, A., Molines, J.-M., Grima, N., Imbard, M., Madec, G., Messager, C., and Michel, S.: An eddy permitting model of the Atlantic circulation: evaluating open boundary conditions, J. Geophys. Res., 106, 22 115–22 129, 2001. Vidal, M., Duarte, C. M., and Agusti, S.: Dissolved organic nitrogen and phosphorus pools and fluxes in the central Atlantic Ocean, Limnol. Oceanogr., 44(1), 106–115, 1999. Williams, G. G. and Follows, M. J.: The Ekman transfer of nutrients and maintenance of new production over the North Atlantic, Deep-Sea Res. Pt I, 45(2–3), 461–489, 1998. Wu, J., Sunda, W., Boyle, E. A., and Karl, D. M.: Phosphate depletion in the western North Atlantic Ocean, Science, 289, 759–762, 2000.