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

• Published in: Biogeosciences
• Main Authors: Lancelot, C, de Montety, A, Goosse, H, Becquevort, S, Schoemann, V, Pasquer, B, Vancoppenolle, M
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2009
• Subjects: Environmental Sciences; Ecological applications; Ecosystem function; East Antarctica; Southern Ocean; Weddell; Weddell Sea; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.5194/bg-6-2861-2009; http://ecite.utas.edu.au/62627

An upgraded version of the biogeochemical modelSWAMCO is coupled to the ocean-sea-ice model NEMOLIMto explore processes governing the spatial distributionof the iron supply to phytoplankton in the Southern Ocean.The 3-D NEMO-LIM-SWAMCO model is implemented inthe ocean domain south of latitude 30 S and runs are performedover September 1989-December 2000. Model scenariosinclude potential iron sources (atmospheric deposition,iceberg calving/melting and continental sediments) aswell as iron storage within sea ice, all formulated based on aliterature review. When all these processes are included, thesimulated iron profiles and phytoplankton bloom distributionsshow satisfactory agreement with observations. Analysesof simulations and sensitivity tests point to the keyrole played by continental sediments as a primary source foriron. Iceberg calving and melting contribute by up to 25% ofChl-a simulated in areas influenced by icebergs while atmosphericdeposition has little effect at high latitudes. Activatingsea ice-ocean iron exchanges redistribute iron geographically.Stored in the ice during winter formation, iron is thentransported due to ice motion and is released and made availableto phytoplankton during summer melt, in the vicinity ofthe marginal ice zones. Transient iron storage and transportassociated with sea ice dynamics stimulate summer phytoplanktonblooming (up to 3 mg Chl-a m-3) in the WeddellSea and off East Antarctica but not in the Ross, Bellingshausenand Amundsen Seas. This contrasted feature resultsfrom the simulated variable content of iron in sea ice and releaseof melting ice showing higher ice-ocean iron fluxes inthe continental shelves of the Weddell and Ross Seas than inthe Eastern Weddell Sea and the Bellingshausen-Amundsen Seas. This study confirms that iron sources and transport inthe Southern Ocean likely provide important mechanisms inthe geographical development of phytoplankton blooms andassociated ecosystems.