Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 6 12 2009 10.5194/bg-6-2829-2009 http://www.biogeosciences.net/6/2829/2009/ http://www.biogeosciences.net/6/2829/2009/bg-6-2829-2009.html http://www.biogeosciences.net/6/2829/2009/bg-6-2829-2009.pdf 2829 2846 2009-12-04 Reconstructing the Nd oceanic cycle using a coupled dynamical – biogeochemical model T. Arsouze arsouze@ldeo.columbia.edu J.-C. Dutay F. Lacan C. Jeandel Laboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA/UVSQ/CNRS, Orme des Merisiers, Gif-Sur-Yvette, Bat 712, 91191 Gif sur Yvette cedex, France Laboratoire d'Etudes en Géophysique et Océanographie Spatiale (LEGOS), UPS/CNES/CNRS/ IRD, Observatoire Midi-Pyrénées, 14 av. E. Belin, 31400 Toulouse, France now at: Lamont-Doherty Earth Observatory (LDEO), P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000, USA The decoupled behaviour observed between Nd isotopic composition (Nd IC, also referred as ε_Nd) and Nd concentration cycles has led to the notion of a "Nd paradox". While ε_Nd behaves in a quasi-conservative way in the open ocean, leading to its broad use as a water-mass tracer, Nd concentration displays vertical profiles that increase with depth, together with a deep-water enrichment along the global thermohaline circulation. This non-conservative behaviour is typical of nutrients affected by scavenging in surface waters and remineralisation at depth. In addition, recent studies suggest the only way to reconcile both concentration and Nd IC oceanic budgets, is to invoke a "Boundary Exchange" process (BE, defined as the co-occurrence of transfer of elements from the margin to the sea with removal of elements from the sea by Boundary Scavenging) as a source-sink term. However, these studies do not simulate the input/output fluxes of Nd to the ocean, and therefore prevents from crucial information that limits our understanding of Nd decoupling. To investigate this paradox on a global scale, this study uses for the first time a fully prognostic coupled dynamical/biogeochemical model with an explicit representation of Nd sources and sinks to simulate the Nd oceanic cycle. Sources considered include dissolved river fluxes, atmospheric dusts and margin sediment re-dissolution. Sinks are scavenging by settling particles. This model simulates the global features of the Nd oceanic cycle well, and produces a realistic distribution of Nd concentration (correct order of magnitude, increase with depth and along the conveyor belt, 65% of the simulated values fit in the ±10 pmol/kg envelop when compared to the data) and isotopic composition (inter-basin gradient, characterization of the main water-masses, more than 70% of the simulated values fit in the ±3 ε_Nd envelop when compared to the data), though a slight overestimation of Nd concentrations in the deep Pacific Ocean may reveal an underestimation of the particle fields by the biogeochemical model. Our results indicate 1) vertical cycling (scavenging/remineralisation) is absolutely necessary to simulate both concentration and ε_Nd, and 2) BE is the dominant Nd source to the ocean. The estimated BE flux (1.1×10¹⁰ g(Nd)/yr) is much higher than both dissolved river discharge (2.6×10⁸ g(Nd)/yr) and atmospheric inputs (1.0×10⁸ g(Nd)/yr) that both play negligible role in the water column but are necessary to reconcile Nd IC in surface and subsurface waters. This leads to a new calculated residence time of 360 yrs for Nd in the ocean. The BE flux requires the dissolution of 3 to 5% of the annual flux of continental weathering deposited via the solid river discharge to the continental margin. % vor jede Referenz Amakawa, H., Nozaki, Y., Alibo, D. S., Zhang, J., Fukugawa, K., and Nagai, H.: Neodymium isotopic variations in Northwest Pacific waters, Geochim. Cosmochim. Ac., 68, 715–727, 2004. Anderson, R. F., Lao, Y., Broecker, W. S., Trumbore, S. E., Hofmann, H. J., and Wolfli, W.: Boundary scavenging in the Pacific Ocean: a comparison of $^10$Be and $^231$Pa, Earth Planet. Sci. Lett., 96, 287–304, 1990. Arsouze, T., Dutay, J. C., Lacan, F., and Jeandel, C.: Modeling the neodymium isotopic composition with a global ocean circulation model, Chem. Geol., 239, 165–177, 2007. Arsouze, T., Dutay, J.-C., Kageyama, M., Lacan, F., Alkama, R., Marti, O., and Jeandel, C.: A modeling sensitivity study of the influence of the Atlantic meridional overturning circulation on neodymium isotopic composition at the Last Glacial Maximum, Clim. Past, 4, 191–203, 2008. Aumont, O., Maier-Reimer, E., Blain, S., and Monfray, P.: An ecosystem model of the global ocean including Fe, Si, P colimitations, Global Biogeochem. Cy., 17(2), 1060, doi:10.1029/2001GB001745, 2003. Aumont, O. and Bopp, L.: Globalizing results from ocean in situ iron fertilization studies, Global Biogeochem. Cy., 20, GB2017, doi:10.1029/2005GB002591, 2006. Bacon, M. P. and Anderson, R. F.: Distribution of thorium isotopes between dissolved and particulate forms in the Deep-Sea., J. Geophys. Res., 87, 2045–2056, 1982. Bayon, G., German, C. R., Burton, K. W., Nesbitt, R. W., and Rogers, N.: Sedimentary Fe-Mn oxyhydroxides as paleoceanographic archives and the role of aeolian flux in regulating oceanic dissolved REE, Earth Planet. Sci. Lett., 224, 477–492, 2004. Bertram, C. J. and Elderfield, H.: The geochemical balance of the rare earth elements and Nd isotopes in the oceans, Geochim. Cosmochim. Ac., 57, 1957–1986, 1993. Blanke, B. and Delecluse, P.: Variability Of The Tropical Atlantic-Ocean Simulated By A General-Circulation Model With 2 Different Mixed-Layer Physics, J. Phys. Oceanogr., 23, 1363–1388, 1993. Boillot, G. and Coulon, C.: La déchirure continentale et l'ouverture océanique - Géologie des marges passives, Overseas Publishers Association eds., Gordon and Breach Science Publishers ed., 1998. Broecker, W. S. and Peng, T. H.: Tracers in the Sea, Eldigio Press, Palisades, NY, 690~pp., 1982. Dahlqvist, R., Andersson, P. S., and Ingri, J.: The concentration and isotopic composition of diffusible Nd in fresh and marine waters, Earth Planet. Sci. Lett., 233, 9–16, 2005. Doney, S. C., Lindsay, K., Caldeira, K., Campin, J. M., Drange, H., Dutay, J. C., Follows, M., Gao, Y., Gnanadesikan, A., Gruber, N., Ishida, A., Joos, F., Madec, G., Maier-Reimer, E., Marshall, J. C., Matear, R. J., Monfray, P., Mouchet, A., Najjar, R., Orr, J. C., Plattner, G. K., Sarmiento, J., Schlitzer, R., Slater, R., Totterdell, I. J., Weirig, M. F., Yamanaka, Y., and Yool, A.: Evaluating global ocean carbon models: The importance of realistic physics, Global Biogeochem. Cy., 18, GB3017, doi:10.1029/2003GB002150, 2004. Duce, R. A., Liss, P. S., Merrill, J. T., Atlas, E. L., Buat-Ménard, P., Hicks, B. B., Miller, J. M., Prospero, J. M., Arimoto, R., Church, T. M., Ellis, W., Galloway, J. N., Hansen, L., Jickells, T. D., Knap, A. H., Reinhardt, K. H., Schneider, B., Soudine, A., Tokos, J. J., Tsunogai, S., Wollast, R., and Zhou, M.: The atmospheric input of trace species to the world ocean, Global Biogeochem. Cy., 5, 193–259, 1991. Dutay, J. C., Bullister, J. L., Doney, S. C., Orr, J. C., Najjar, R., Caldeira, K., Campin, J. M., Drange, H., Follows, M., Gao, Y., Gruberi, N., Hecht, M. W., Ishida, A., Joos, F., Lindsay, K., Madec, G., Maier-Reimer, E., Marshall, J. C., Matear, R. J., Monfray, P., Mouchet, A., Plattner, G.-K., Sarmiento, J., Schlitzer, R., Slater, R., Totterdell, I. J., Weirig, M.-F., Yamanaka, Y., and Yool, A.: Evaluation of ocean model ventilation with CFC-11: comparison of 13 global ocean models, Ocean Model., 42, 89–120, 2002. Dutay, J. C., Jean-Baptiste, P., Campin, J. M., Ishida, A., Maier-Reimer, E., Matear, R. J., Mouchet, A., Totterdell, I. J., Yamanaka, Y., Rodgers, K., Madec, G., and Orr, J. C.: Evaluation of OCMIP-2 ocean models' deep circulation with mantle helium-3, J. Marine Syst., 48, 15–36, 2004. Dutay, J.-C., Lacan, F., Roy-Barman, M., and Bopp, L.: Influence of particle size and type on 231 Pa and 230 Th simulation with a global coupled biogeochemical-ocean general circulation model: A first approach, Geochem. Geophy. Geosy., 10, Q01011, doi:10.1029/2008GC002291, 2009. Elderfield, H.: The oceanic chemistry of the Rare Earth Elements, Philos. T. Roy. Soc. Lond., 325, 105–106, 1988. Elderfield, H., Upstill-Goddard, R., and Sholkovitz, E. R.: The rare earth elements in rivers, estuaries, and coastal seas and their significance to the composition of ocean waters, Geochim. Cosmochim. Ac., 54, 971–991, 1990. Fichefet, T. and Maqueda, M. A. M.: Sensitivity of a global sea ice model to the treatment of ice thermodynamics and dynamics, J. Geophys. Res.-Oceans, 102, 12609–12646, 1997. Gehlen, M., Bopp, L., Emprin, N., Aumont, O., Heinze, C., and Ragueneau, O.: Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model, Biogeosciences, 3, 521–537, 2006. Gent, P. R. and McWilliams, J. C.: Isopycnal Mixing In Ocean Circulation Models, J. Phys. Oceanogr., 20, 150–155, 1990. GEOTRACES: An international study of the marine biogeochemical cycles of trace elements and isotopes, online available at: http://www.geotraces.org/, 2005. Goldstein, S. L., O'Nions, R. K., and Hamilton, P. J.: A Sm-Nd study of atmospheric dusts and particulates from major river systems, Earth Planet. Sci. Lett., 70, 221–236, 1984. Goldstein, S. L. and Jacobsen, S. B.: The Nd and Sr isotopic systematics of river-water dissolved material: implications for the sources of Nd and Sr in the seawater, Chem. Geol. (Isotope Geosc. Section), 66, 245–272, 1987. Goldstein, S. L. and Hemming, S. R.: Long lived Isotopic Tracers in Oceanography, Paleoceanography, and Ice sheet dynamics, in: Treatise on Geochemistry, edited by: Elderfield, H., Elsevier Pergamon press, Amsterdam, chapter~6.17, 2003. Greaves, M. J., Statham, P. J., and Elderfield, H.: Rare earth element mobilization from marine atmospheric dust into seawater, Mar. Chem., 46, 255–260, 1994. Grousset, F., Parra, M., Bory, A., Martinez, P., Bertrand, P., Shiemmield, G., and Ellam, R. M.: Saharan wind regimes traced by the Sr-Nd isotopic composition of subtropical Atlantic Sediments: last glacial maximum vs. today, Quaternary Sci. Rev., 17, 395–409, 1998. Grousset, F. E., Biscaye, P. E., Zindler, A., Prospero, J., and Chester, R.: Neodymium isotopes as tracers in marine sediments and aerosols: North Atlantic, Earth Planet. Sci. Lett., 87, 367–378, 1988. Gutjahr, M., Frank, M., Stirling, C. H., Keigwin, L. D., and Halliday, A. N.: Tracing the Nd isotope evolution of North Atlantic deep and intermediate waters in the Western North Atlantic since the Last Glacial Maximum from Blake Ridge sediments, Earth Planet. Sci. Lett., 266, 61–77, 2008. Henderson, G. M., Heinze, C., Anderson, R. F., and Winguth, A. M. E.: Global distribution of the Th-230 flux to ocean sediments constrained by GCM modelling, Deep-Sea Res. I, 46, 1861–1893, 1999. Jeandel, C.: Concentration and isotopic composition of Nd in the South Atlantic Ocean, Earth Planet. Sci. Lett., 117, 581–591, 1993. Jeandel, C., Bishop, J. K., and Zindler, A.: Exchange of Nd and its isotopes between seawater small and large particles in the Sargasso Sea, Geochim. Cosmochim. Ac., 59, 535–547, 1995. Jeandel, C., Thouron, D., and Fieux, M.: Concentrations and Isotopic compositions of Nd in the Eastern Indian Ocean and Indonesian Straits, Geochim. Cosmochim. Ac., 62, 2597–2607, 1998. Jeandel, C., Arsouze, T., Lacan, F., Techine, P., and Dutay, J. C.: Isotopic Nd compositions and concentrations of the lithogenic inputs into the ocean: A compilation, with an emphasis on the margins, Chem. Geol., 239, 156–164, 2007. Johannesson, K. H. and Burdige, D. J.: Balancing the global oceanic neodymium budget: Evaluating the role of groundwater, Earth Planet. Sci. Lett., 253, 129–142, 2007. Jones, K., Khatiwala, S., Goldstein, S. L., Hemming, S. R., and Van de Flierdt, T.: Modeling the distribution of Nd isotopes in the oceans using an offline Ocean General Circulation Model, Earth Planet. Sci. Lett., 202(3–4), 610–619, 2008. Khatiwala, S., Visbeck, M., and Cane, M. A.: Accelerated simulation of passive tracers in ocean circulation models, Ocean Model., 9, 51–69, 2005. Kriest, I.: Different parameterizations of marine snow in a 1D-model and their influence on representation of marine snow, nitrogen budget and sedimentation, Deep-Sea Res. I, 49, 2133–2162, 2002. Lacan, F. and Jeandel, C.: Tracing Papua New Guinea imprint on the central Equatorial Pacific Ocean using neodymium isotopic compositions and Rare Earth Element patterns, Earth Planet. Sci. Lett., 186, 497–512, 2001. Lacan, F. and Jeandel, C.: Subpolar Mode Water formation traced by neodymium isotopic composition, Geophys. Res. Lett., 31, L14306, doi:10.1029/2004GL019747, 2004. Lacan, F. and Jeandel, C.: Neodymium isotopes as a new tool for quantifying exchange fluxes at the continent – ocean interface, Earth Planet. Sci. Lett., 232, 245–257, 2005. Madec, G.: NEMO reference manual, ocean dynamics component : NEMO-OPA. Preliminary version, Note du Pole de modélisation, Institut Pierre-Simon Laplace (IPSL), 27, 2006. Monod, J.: Recherches sur la croissance des cultures bactériennes, Hermann, Paris, 1942. Milliman, J. D. and Syvitski, J. P. M.: Geomorphic/tectonic control of sediment discharge to the ocean: the importance of small mountain rivers, J. Geol., 100, 325–344, 1992. Nozaki, Y., Horibe, Y., and Tsubota, H.: The water column distribution of thorium isotopes in the western North Pacific, Earth Planet. Sci. Lett., 54, 203–216, 1981. Nozaki, Y. and Zhang, J.: The rare earth elements and yttrium in the coastal/offshore mixing zone of Tokyo Bay waters and Kuroshio, Biogeochemical Processes and Ocean Flux in the Western Pacific, edited by: Sakai, H. and Nozaki, Y., 171–184, 1995. Nozaki, Y. and Alibo, D.: Importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern Indian Ocean, Earth Planet. Sci. Lett., 205, 155–172, 2003. Oka, A., Kato, S., and Hasumi, H.: Evaluating effect of ballast mineral on deep-ocean nutrient concentration by using an ocean general circulation model, Global Biogeochem. Cy., 22, GB3004, doi:10.1029/2007GB003067, 2008. Piepgras, D. J., Wasserburg, G. J., and Dasch, E. G.: The isotopic composition of Nd in different ocean masses, Earth Planet. Sci. Lett., 45, 223–236, 1979. Piepgras, D. J. and Wasserburg, G. J.: Neodymium isotopic variations in seawater, Earth Planet. Sci. Lett., 50, 128–138, 1980. Piepgras, D. J. and Wasserburg, G. J.: Isotopic composition of neodymium in waters from the Drake Passage, Science, 217, 207–217, 1982. Piepgras, D. J. and Wasserburg, G. J.: Influence of the Mediterranean outflow on the isotopic composition of neodymium in waters of the North Atlantic, J. Geophys. Res., 88, 5997–6006, 1983. Piepgras, D. J. and Wasserburg, G. J.: Rare earth element transport in the western North Atlantic inferred from isotopic observations, Geochim. Cosmochim. Ac., 51, 1257–1271, 1987. Piotrowski, A. M., Goldstein, S. L., Hemming, S. R., and Fairbanks, R. G.: Intensification and variability of ocean thermohaline circulation through the last deglaciation, Earth Planet. Sci. Lett., 225, 205–220, 2004. Rickli, J., Frank, M., and Haliday, A. N.: The Halfnium-neodymium isotopic composition of Atlantic seawater, Earth Planet Sci. Lett., 280, 118–127, 2009. Rutberg, R. L., Hemming, S. R., and Goldstein, S. L.: Reduced North Atlantic deep Water flux to the glacial Southern Ocean inferred from neodymium isotope ratios, Nature, 405, 935–938, 2000. Shimizu, H., Tachikawa, K., Masuda, A., and Nozaki, Y.: Cerium and neodymium ratios and REE patterns in seawater from the North Pacific Ocean, Geochim. Cosmochim. Ac., 58, 323–333, 1994. Sholkovitz, E., Landing, W., and Lewis, B.: Ocean particle chemistry: The fractionation of Rare Earth Elements between suspended particles and seawater, Geochim. Cosmochim. Ac., 58, 1567–1579, 1994. Sholkovitz, E. R.: The geochemistry of rare earth elements in the Amazon River estuary, Geochim. Cosmochim. Ac., 57, 2181–2190, 1993. Siddall, M., Henderson, G. M., Edwards, N. R., Frank, M., Muller, S. A., Stocker, T. F., and Joos, F.: Pa-231/Th-210 fractionation by ocean transport, biogenic particle flux and particle type, Earth Planet. Sci. Lett., 237, 135–155, 2005. Siddall, M., Khatiwala, S., Van de Flierdt, T., Jones, K., Goldstein, S. L., Hemming, S. R., and Anderson, R. F.: Towards explaining the Nd paradox using reversible scavenging and the Transport Matrix Method, Earth Planet. Sci. Lett., 274, 448–461, 2008. Stordal, M. C. and Wasserburg, G. J.: Neodymium isotopic study of Baffin Bay water: sources of REE from very old terranes, Earth Planet. Sci. Lett., 77, 259–272, 1986. Tachikawa, K., Jeandel, C., and Dupré, B.: Distribution of rare earth elements and neodymium isotopes in settling particulate material of the tropical Atlantic Ocean (EUMELI site), Deep-Sea Res., 44, 1769–1792, 1997. Tachikawa, K., Jeandel, C., and Roy-Barman, M.: A new approach to Nd residence time in the ocean: the role of atmospheric inputs, Earth Planet. Sci. Lett., 170, 433–446, 1999. Tachikawa, K., Athias, V., and Jeandel, C.: Neodymium budget in the ocean and paleoceanographic implications, J. Geophys. Res., 108, 3254 doi:3210.1029/1999JC000285, 2003. Tegen, I. and Fung, I.: Contribution to the atmospheric mineral aerosol load from land surface modification, J. Geophys. Res., 100, 18707–18726, 1995. Timmermann, R., Goosse, H., Madec, G., Fichefet, T., Ethe, C., and Duliere, V.: On the representation of high latitude processes in the ORCA-LIM global coupled sea ice-ocean model, Ocean Model., 8, 175–201, 2005. Van De Flierdt, T., Frank, M., Lee, D. C., Halliday, A. N., Reynolds, B. C., and Hein, J. R.: New constraints on the sources and behavior of neodymium and hafnium in seawater from Pacific Ocean ferromanganese crusts, Geochim. Cosmochim. Ac., 68, 3827–3843, 2004. von Blanckenburg, F., O'Nions, P. K., Belshaw, N. S., Gibb, A., and Hein, J. R.: Global distribution of beryllium isotopes in deep ocean water as derived from Fe-Mn crusts, Earth Planet. Sci. Lett., 141, 213–226, 1996. von Blanckenburg, F.: Perspectives: Paleoceanography – Tracing past ocean circulation?, Science, 286, 1862–1863, 1999. Zhang, Y., Lacan, F., and Jeandel, C.: Dissolved rare earth elements tracing lithogenic inputs over the Kerguelen Plateau (Southern Ocean), Deep-Sea Res. II, 55, 638–652, 2008.