Spatial distribution of the iron supply to phytoplankton in the Southern Ocean: a model study

Abstract. An upgraded version of the biogeochemical model SWAMCO is coupled to the ocean-sea-ice model NEMO-LIM to explore processes governing the spatial distribution of the iron supply to phytoplankton in the Southern Ocean. The 3-D NEMO-LIM-SWAMCO model is implemented in the ocean domain south of latitude 30° S and runs are performed over September 1989–December 2000. Model scenarios include potential iron sources (atmospheric deposition, iceberg calving/melting and continental sediments) as well as iron storage within sea ice, all formulated based on a literature review. When all these processes are included, the simulated iron profiles and phytoplankton bloom distributions show satisfactory agreement with observations. Analyses of simulations and sensitivity tests point to the key role played by continental sediments as a primary source for iron. Iceberg calving and melting contribute by up to 25% of Chl-a simulated in areas influenced by icebergs while atmospheric deposition has little effect at high latitudes. Activating sea ice-ocean iron exchanges redistribute iron geographically. Stored in the ice during winter formation, iron is then transported due to ice motion and is released and made available to phytoplankton during summer melt, in the vicinity of the marginal ice zones. Transient iron storage and transport associated with sea ice dynamics stimulate summer phytoplankton blooming (up to 3 mg Chl-a m-3 in the Weddell Sea and off East Antarctica but not in the Ross, Bellingshausen and Amundsen Seas. This contrasted feature results from the simulated variable content of iron in sea ice and release of melting ice showing higher ice-ocean iron fluxes in the continental shelves of the Weddell and Ross Seas than in the Eastern Weddell Sea and the Bellingshausen-Amundsen Seas. This study confirms that iron sources and transport in the Southern Ocean likely provide important mechanisms in the geographical development of phytoplankton blooms and associated ecosystems.

[1]  Jian Zhang.  Influence of the Southern Annular Mode on the sea ice-ocean system , 2010 .

[2]  J. Tison,et al.  Modelling brine and nutrient dynamics in Antarctic sea ice: the case of dissolved silica , 2009 .

[3]  J. Schwarz,et al.  Impact of drifting icebergs on surface phytoplankton biomass in the Southern Ocean: Ocean colour remote sensing and in situ iceberg tracking , 2009 .

[4]  L. Bopp,et al.  Evaluating the importance of atmospheric and sedimentary iron sources to Southern Ocean biogeochemistry , 2009 .

[5]  Richard S. Lampitt,et al.  Southern Ocean deep-water carbon export enhanced by natural iron fertilization , 2009, Nature.

[6]  P. Mathiot.  Influence du forçage atmosphérique sur la représentation de la glace de mer et des eaux de plateau en Antarctique dans une étude de modélisation numérique , 2009 .

[7]  C. Mordy,et al.  Sea ice‐derived dissolved iron and its potential influence on the spring algal bloom in the Bering Sea , 2008 .

[8]  K. Arrigo,et al.  Primary production in the Southern Ocean, 1997–2006 , 2008 .

[9]  N. Mahowald,et al.  Revisiting atmospheric dust export to the Southern Hemisphere ocean: Biogeochemical implications , 2008 .

[10]  S. Tulaczyk,et al.  Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt , 2008, Geochemical transactions.

[11]  Olivier Aumont,et al.  Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition , 2007 .

[12]  J. K. Moore,et al.  Wind speed influence on phytoplankton bloom dynamics in the Southern Ocean Marginal Ice Zone , 2007 .

[13]  Kenneth L. Smith,et al.  Free-Drifting Icebergs: Hot Spots of Chemical and Biological Enrichment in the Weddell Sea , 2007, Science.

[14]  J. Tison,et al.  Distribution and biogeochemical behaviour of iron in the East Antarctic sea ice , 2007 .

[15]  H. Goosse,et al.  Analysis of the projected regional sea-ice changes in the Southern Ocean during the twenty-first century , 2007 .

[16]  B. Quéguiner,et al.  Effect of natural iron fertilization on carbon sequestration in the Southern Ocean , 2007, Nature.

[17]  J. K. Moore,et al.  Sedimentary and mineral dust sources of dissolved iron to the World Ocean , 2007 .

[18]  J. K. Moore,et al.  Observations of dissolved iron concentrations in the World Ocean: implications and constraints for ocean biogeochemical models , 2007 .

[19]  C. Moulin,et al.  Interannual variability of dimethylsulfide in air and seawater and its atmospheric oxidation by‐products (methanesulfonate and sulfate) at Dumont d'Urville, coastal Antarctica (1999–2003) , 2007 .

[20]  E. Boyle,et al.  Mesoscale Iron Enrichment Experiments 1993-2005: Synthesis and Future Directions , 2007, Science.

[21]  P. Statham,et al.  The Crozet natural iron bloom and export experiment (CROZEX). Special issue , 2007 .

[22]  Gregory G. Leptoukh,et al.  Online analysis enhances use of NASA Earth science data , 2007 .

[23]  L. Bopp,et al.  Globalizing results from ocean in situ iron fertilization studies , 2006 .

[24]  K. Arrigo,et al.  Processes governing the supply of iron to phytoplankton in stratified seas , 2006 .

[25]  S. Fan,et al.  Aeolian input of bioavailable iron to the ocean , 2006 .

[26]  J. Tison,et al.  Development of a sampling and flow injection analysis technique for iron determination in the sea ice environment , 2006 .

[27]  N. Mahowald,et al.  Atmospheric global dust cycle and iron inputs to the ocean , 2005 .

[28]  H. Goosse,et al.  Influence of the Southern Annular Mode on the sea ice-ocean system: the role of the thermal and mechanical forcing , 2005 .

[29]  Ulf Riebesell,et al.  Synthesis of iron fertilization experiments: From the iron age in the age of enlightenment , 2005 .

[30]  M. Grotti,et al.  Trace metals distributions in coastal sea ice of Terra Nova Bay, Ross Sea, Antarctica , 2005, Antarctic Science.

[31]  Edward A. Boyle,et al.  Decoupling of iron and phosphate in the global ocean , 2005 .

[32]  N. Mahowald,et al.  Global Iron Connections Between Desert Dust, Ocean Biogeochemistry, and Climate , 2005, Science.

[33]  Stephanie Dutkiewicz,et al.  Interactions of the iron and phosphorus cycles: A three‐dimensional model study , 2005 .

[34]  Xiujun Wang,et al.  The distribution and behavior of dissolved and particulate iron and zinc in the Ross Sea and Antarctic circumpolar current along 170°W , 2005 .

[35]  S. Baines,et al.  Cellular iron contents of plankton during the Southern Ocean Iron Experiment (SOFeX) , 2004 .

[36]  Daniele Iudicone,et al.  Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology , 2004 .

[37]  Keith Lindsay,et al.  Upper ocean ecosystem dynamics and iron cycling in a global three‐dimensional model , 2004 .

[38]  Peter Rothery,et al.  Long-term decline in krill stock and increase in salps within the Southern Ocean , 2004, Nature.

[39]  M. Öztürk,et al.  The distribution and speciation of iron along 6°E in the Southern Ocean , 2004 .

[40]  K. Timmermans,et al.  Growth rates, half‐saturation constants, and silicate, nitrate, and phosphate depletion in relation to iron availability of four large, open‐ocean diatoms from the Southern Ocean , 2004 .

[41]  T. Fichefet,et al.  Influence of the Southern Annular Mode on the sea ice-ocean system: the role of the thermal and mechanical forcing , 2005 .

[42]  T. Fichefet,et al.  Utilizing the ASPeCt sea ice thickness data set to evaluate a global coupled sea ice-ocean model , 2004 .

[43]  K. Coale,et al.  The flux of iron from continental shelf sediments: A missing source for global budgets , 2004 .

[44]  Antonietta Quigg,et al.  THE ELEMENTAL COMPOSITION OF SOME MARINE PHYTOPLANKTON 1 , 2003 .

[45]  Watson W. Gregg,et al.  Phytoplankton and iron: validation of a global three-dimensional ocean biogeochemical model , 2003 .

[46]  N. Mahowald,et al.  Sensitivity study of meteorological parameters on mineral aerosol mobilization, transport, and distribution , 2003 .

[47]  Elizabeth C. Kent,et al.  Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century , 2003 .

[48]  Stéphane Blain,et al.  An ecosystem model of the global ocean including Fe, Si, P colimitations , 2003 .

[49]  H. Goosse,et al.  Linking ocean biogeochemical cycles and ecosystem structure and function: results of the complex SWAMCO-4 model , 2003 .

[50]  H. Hellmer,et al.  Simulations of ice‐ocean dynamics in the Weddell Sea 1. Model configuration and validation , 2002 .

[51]  Aike Beckmann,et al.  Simulations of ice-ocean dynamics in the Weddell Sea 2. Interannual variability 1985-1993 , 2002 .

[52]  M. Chin,et al.  Sources and distributions of dust aerosols simulated with the GOCART model , 2001 .

[53]  Rupert Gladstone,et al.  Iceberg trajectory modeling and meltwater injection in the Southern Ocean , 2001 .

[54]  P. Croot,et al.  Organic complexation of iron in the Southern Ocean , 2001 .

[55]  K. Johnson.  Iron supply and demand in the upper ocean: Is extraterrestrial dust a significant source of bioavailable iron? , 2001 .

[56]  M. Abbott,et al.  Phytoplankton chlorophyll distibutions and primary production in the Southern Ocean , 2000 .

[57]  Keith M. Hines,et al.  Artificial surface pressure trends in the NCEP-NCAR reanalysis over the Southern Ocean and Antarctica , 2000 .

[58]  E. Boyle,et al.  Glacial/interglacial variations in atmospheric carbon dioxide , 2000, Nature.

[59]  Christiane Lancelot,et al.  Modeling phytoplankton blooms and carbon export production in the Southern Ocean : dominant controls by light and iron in the Atlantic sector in Austral spring 1992 , 2000 .

[60]  C. V. D. Berg,et al.  Iron availability and the release of iron-complexing ligands by Emiliania huxleyi , 2000 .

[61]  S. Doney,et al.  Iron supply and demand in the upper ocean , 2000 .

[62]  B. Quéguiner,et al.  Limitation of algal growth by iron deficiency in the Australian Subantarctic Region , 1999 .

[63]  K. Timmermans,et al.  Low dissolved Fe and the absence of diatom blooms in remote Pacific waters of the Southern Ocean , 1999 .

[64]  W. Merryfield,et al.  A Global Ocean Model with Double-Diffusive Mixing , 1999 .

[65]  G. Kattner,et al.  Dissolved iron at subnanomolar levels in the Southern Ocean as determined by ship-board analysis , 1998 .

[66]  Kevin R. Arrigo,et al.  Primary production in Southern Ocean waters , 1998 .

[67]  P. Sedwick,et al.  Regulation of algal blooms in Antarctic Shelf Waters by the release of iron from melting sea ice , 1997 .

[68]  Edward A. Boyle,et al.  What controls dissolved iron concentrations in the world ocean? — a comment , 1997 .

[69]  M. Maqueda,et al.  Sensitivity of a global sea ice model to the treatment of ice thermodynamics and dynamics , 1997 .

[70]  R. Döscher,et al.  A Method for Improved Representation of Dense Water Spreading over Topography in Geopotential-Coordinate Models , 1997 .

[71]  Phillip A. Arkin,et al.  Analyses of Global Monthly Precipitation Using Gauge Observations, Satellite Estimates, and Numerical Model Predictions , 1996 .

[72]  Inez Y. Fung,et al.  Contribution to the atmospheric mineral aerosol load from land surface modification , 1995 .

[73]  T. McDougall,et al.  Minimal Adjustment of Hydrographic Profiles to Achieve Static Stability , 1995 .

[74]  V. Smetácek,et al.  Importance of iron for plankton blooms and carbon dioxide drawdown in the Southern Ocean , 1995, Nature.

[75]  Bruno Blanke,et al.  Variability of the Tropical Atlantic Ocean Simulated by a General Circulation Model with Two Different Mixed-Layer Physics , 1993 .

[76]  C. Lancelot,et al.  Factors controlling phytoplankton ice-edge blooms in the marginal ice-zone of the northwestern Weddell Sea during sea ice retreat 1988: Field observations and mathematical modelling , 1993, Polar Biology.

[77]  P. Falkowski,et al.  Effect of iron limitation on photosynthesis in a marine diatom , 1991 .

[78]  B. Mitchell,et al.  Light limitation of phytoplankton biomass and macronutrient utilization in the Southern Ocean , 1991 .

[79]  R. Duce,et al.  Atmospheric transport of iron and its deposition in the ocean , 1991 .

[80]  R. F. Nolting,et al.  Cadmium, copper and iron in the Scotia Sea, Weddell Sea and Weddell/Scotia Confluence (Antarctica) , 1991 .

[81]  C. Lancelot,et al.  Modelling ice-edge phytoplankton bloom in the Scotia-Weddell sea sector of the Southern Ocean during spring 1988 , 1991 .

[82]  P. Tréguer,et al.  On iron limitation of the Southern Ocean : experimental observations in the Weddell and Scotia Seas. , 1990 .

[83]  D. M. Nelson,et al.  Phytoplankton Bloom Produced by a Receding Ice Edge in the Ross Sea: Spatial Coherence with the Density Field , 1985, Science.

[84]  W. Hibler.  A Dynamic Thermodynamic Sea Ice Model , 1979 .

[85]  A. Semtner.  A MODEL FOR THE THERMODYNAMIC GROWTH OF SEA ICE IN NUMERICAL INVESTIGATIONS OF CLIMATE , 1975 .

[86]  Frank O. Bryan,et al.  Coordinated Ocean-ice Reference Experiments (COREs) , 2009 .

[87]  Sylvain Bouillon,et al.  Simulating the mass balance and salinity of Arctic and Antarctic sea ice. 1. Model description and validation , 2009 .

[88]  J. Tison,et al.  Iron study during a time series in the western Weddell pack ice , 2008 .

[89]  G. Madec.  NEMO ocean engine , 2008 .

[90]  Valérie Dulière,et al.  On the representation of high latitude processes in the ORCA-LIM global coupled sea ice–ocean model , 2005 .

[91]  R. Zeebe.  Glacial/interglacial variations in atmospheric CO2 , 2002 .

[92]  Koji Suzuki,et al.  The distribution of Fe in the Australian sector of the Southern Ocean , 2000 .

[93]  K. Johnson,et al.  Trace metal concentrations in the Ross Sea and their relationship with nutrients and phytoplankton growth , 2000 .

[94]  P. Delecluse,et al.  OPA 8.1 Ocean General Circulation Model reference manual , 1998 .

[95]  F. Dehairs,et al.  The distribution of Fe in the antarctic circumpolar current , 1997 .

[96]  Ming L Ia.  Mixed Layer Deepening Due to Langmuir Circulation , 1997 .

[97]  P. Gent,et al.  Isopycnal mixing in ocean circulation models , 1990 .