1. The impact of (sub-)mesoscale eddies on the soft-tissue carbon pump Anne Willem Omta Bas Kooijman Theoretical Life Sciences, Vrije Universiteit (Amsterdam) Henk Dijkstra IMAU, Universiteit Utrecht www.bio.vu.nl/thb Grant No. 635.100.009 (Computational Life Sciences)

2. The soft-tissue carbon pump

3. Ocean eddy field Real ocean eddy field very complicated: simulate one single eddy for better understanding

4. Flow model Non-hydrostatic 3-D model Domain 32 km * 32 km * 1 km Periodic boundary conditions

5. Phytoplankton Internal Nitrogen and Carbon (PINC) model PINC organisms consist of: biomass structure (91% C, 9% N) carbon reserve (100% C) nitrogen reserve (100% N) Ratio of components determines C:N ratio of organisms

6. Initial conditions Biomass: –C:N ratio of 11:1 –Sinking of organic carbon and nitrogen balanced by upward diffusion of DIC and DIN Eddy radius ~8 km, no vertical velocity

7. Vertical velocity patterns 3.6 days 7.2 days 12 days

8. Plankton distributions Upwelling of DIN leads to strong biomass increase, first in lobes, later also in centre of eddy 7.2 days 12 days

9. Net effect on DIC/DIN after 12 days DIN and DIC increase, because not all the upwelled DIN and DIC are consumed DIC decrease DIN increase DIN decrease DIC increase

10. C:N ratio (R) R decreases in time, because organisms receive more N

11. The submesoscale eddy weakens the soft- tissue carbon pump, because: Not all the upwelling DIN is consumed - could also be shown with fixed-stoichiometry plankton model The C:N ratio of phytoplankton decreases - could only shown with flexible-stoichiometry plankton model Conclusion More information: www.bio.vu.nl/thb