The impact of submesoscale eddies on the softtissue

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)

The soft-tissue carbon pump

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

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

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

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

Vertical velocity patterns 7. 2 days 3. 6 days 12 days

Plankton distributions 7. 2 days 12 days Upwelling of DIN leads to strong biomass increase, first in lobes, later also in centre of eddy

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

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

Conclusion The submesoscale eddy weakens the softtissue 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 More information: www. bio. vu. nl/thb