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m.racault@uea.ac.uk

Changes in the Southern Ocean biological export production over the period 1968-2004. Marie-F. Racault, Corinne Le Quéré & Erik Buitenhuis CARBOOCEAN Annual Meeting Gran Canaria, December 2006. m.racault@uea.ac.uk.

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m.racault@uea.ac.uk

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  1. Changes in the Southern Ocean biological export production over the period 1968-2004 Marie-F. Racault, Corinne Le Quéré & Erik Buitenhuis CARBOOCEAN Annual Meeting Gran Canaria, December 2006 m.racault@uea.ac.uk

  2. Strengthening and poleward shifting of the winds in the Southern Ocean NCEP winds (m/s) 2004 mean 2004 minus 1967

  3. Decrease in the Southern Ocean sink of CO2 expected observations modelled

  4. Carbon content (PgC/y) of the Southern Ocean Changes in Export and Primary Production? Total ΔFCO2 = 0.15 Atmosphere ΔFHeat = 0.01 Euphotic zone ΔPP = ? ΔExp = ? Deep ocean ΔDIC = 0.4PgC/y ΔDIC = ?

  5. OPA model • OPA General Circulation model • 0.5-1.5ox2o resolution • 31 vertical levels • Calculated vertical mixing • NCEP daily forcing

  6. PISCES-T model • PISCES-T ecosystem model • 2 phyto, 2 zoo., 2 sinking particles • Limitation by Fe, P, and Si • Initialise with observations in 1948 (Buitenhuis et al., GBC 2006)

  7. Chla (mg/m3) and biological export production (molC/m2/y) from the model and based on observations PISCES-T bio. export PISCES-T Chla SeaWiFS Chla Obs. bio. export * * Schlitzer, 2002

  8. eratio in the Southern Ocean over the period 1968-2004 mean eratio mean Export Production (PgC/y) 1.4 Exp = 0.3 PP Primary Production (PgC/y) 4.7 Southern Ocean eratio

  9. eratio in the Southern Ocean (SO) vs. Global Ocean Exp = 0.3 PP SO mean global mean SO mean eratio global mean eratio Export Production (PgC/y) 1.4 8.9 Exp = 0.15 PP Primary Production (PgC/y) 4.7 61 Global eratio SO

  10. Have the changes in circulation induced a trend in the biological export production? Simulation of PISCES-T with observed atmospheric forcing • OPA General Circulation model • 0.5-1.5ox2o resolution • 31 vertical levels • Calculated vertical mixing • NCEP daily forcing

  11. Have the changes in circulation induced a trend in the biological export production? Simulation of PISCES-T with constant atmospheric forcing • OPA General Circulation model • 0.5-1.5ox2o resolution • 31 vertical levels • Calculated vertical mixing • NCEP daily forcing from year 1967 repeated onward

  12. Trend in the Southern Ocean Chla (mg/m3) Time series of the Chla induced by changes in circulation PISCES-T with obs.atmo. forcing minusPISCES-T with constantforcing Increase of 0.07 mgChl/m3 over 38 years

  13. Increase in the eratio in the Southern Ocean caused by changes in circulation ΔExp = 0.57 ΔPP mean changes mean eratio ΔExport Production (PgC/y) 0.3 = 0.3 ΔPrimary Production (Pgc/y) 0.6 PISCES-T eratio withobs. atmo. forcing minus PISCES-T eratio with constant forcing eratio due to changes in circulation

  14. Carbon content (PgC/y) of the Southern Ocean Increase in Export and Primary Production Total ΔFCO2 = 0.15 Atmosphere ΔFHeat = 0.01 Euphotic zone ΔPP = 0.6 ΔExp = 0.3 Deep ocean ΔDIC = 0.4PgC/y ΔDIC = 0.4

  15. Conclusions High eratio in the Southern Ocean Export production compensates 3/4 of the DIC Model results supported by observations Further work Investigate the structure of the ecosystem and estimate its role in this context of circulation changes

  16. Further modelling studies Prototype version of PLANKTON 10 currently working Light Si PO4 NO3 DMS NH4 Fe Picophyto plankton Nanophyto plankton Coccolitho-phorids Phaeocystis N2 fixers Diatoms Bacteria CaCO3 DOM Microzoo-plankton Zoopl. filter feeders Mesozoo-plankton

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