1. Quantifying competing carbon pathways in mesoscale upwelling filaments off NW Africa Nick Hardman-Mountford (CSIRO), Carol Robinson (UEA), Ricardo Torres, Tim Smyth, Ian Brown, Vasilis Kitidis, P. Nightingale, C. Widdicombe (PML) (or the pitfalls of seawater CO 2 inversions)

2. What is relative contribution of different CO 2 pathways: air-sea flux vs. export production? NCP = E

3. Lagrangian study: plume tracking with SF 6 and drifters 3 patches seeded P1 & P3 filaments tracked P2 subducted SOLAS-ICON + (D338) + The impact of coastal upwelling on the air-sea exchange of climatically important gases Rees et al. 2011

4. Sampling Underway: T, S, fCO 2, O 2, Fl Surface drifters: T, S, fCO 2 Physics: CTD, MVP, ADCP, micro-turbulence, wirewalker, optics Rosette bottle samples Deck incubations

5. Spatial structure – satellite view Patch 1: freshly upwelled, followed for 9 days Patch 3: ~10 days old, followed for 8 days

6. Spatial structure – in situ

7. Temporal variability

8. Phytoplankton community and primary production Patch 1 Patch 3

9. Daily DIC change Sea-air Flux Vertical diffusion flux Horizontal diffusion flux Vertical entrainment (ventilation) Horizontal advection NCP Assume advection/diffusion terms negligible because lagrangian expt, i.e. tracking water patch. Supported by lack of relationship between salinity and DIC within patch Salinity normalise DIC to make sure ? Controls on CO 2 dynamics Shadwick et al. 2010 Focus on NCP, F and V?

10. DIC calculations Need continuous DIC Use discrete TA / S relationship to calculate continuous TA s Calculate DIC from TA s and measured underway fCO 2 in CO 2 SYS Salinity normalise calculated DIC = nDIC

11. Daily δnDIC calculation δnDIC day δnDIC night δnDIC day+night nDIC Time depth integrated NCP t = Z eu t (max DIC t - max DIC t-1 ) – F t (– V t )

12. A. Daily nDIC change Patch 1 Patch 3 Daily DIC reduction Night time DIC increase  production/respiration signal Patch 1 has larger signals and is more variable than Patch 3

13. B. Sea-air CO 2 fluxes Patch 1 Patch 3 Calculated using Nightingale et al. (2000) Winds 6-14 m s -1 P1, 8-14 m s -1 P3 ΔpCO2 20-100 µatm P1, 60-110 µatm P3 Patch 1 sea-air flux starts high and reduces as seawater pCO 2 reduces Increase on 25-26/4 from ventilation? Patch 3 sea-air flux higher on average, more gradual decline, driven by seawater pCO 2 decline

14. C. Depth Integrated NCP* vs. sea-air flux Patch 1 Patch 3 Louicades et al. 2011 Patch 1

15. C. Depth Integrated NCP* vs. sea-air flux Patch 1 Patch 3 Patch 1 is net autotrophic and NCP* dominates over sea-air flux Patch 3 shifts from autotrophic to heterotrophic between days In ~trophic balance over all NCP* dominates the signal but overall sea-air flux is greater mmol C m -2 Patch 1Patch 3 NCP*128529 Sea-air flux 86124

16. NACW>50% Max(80%,75m) SACW>50 % Max(95%,300m) SACW<50% Max(40%,150m) (NACW or BDA shelf water) SACW>50 % (Max 100%) Patch 1 Patch 3 Water masses

17. D. NCP vs. entrainment/ventilation vs. sea-air flux Use change in nutricline depth and DIC gradient over nutricline NCP (residual) has to increase with ventilation Accounting for ventilation increases estimate of autotrophy - Is it real? mmol C m -2 Patch 1Patch 3 NCP-V 2823715 Vent 1537687 Sea-air flux 86124

18. Preliminary conclusions 1.Biogeochemistry different between filaments: – phytoplankton, CO 2 dynamics, [nutrients] – Water masses or age? 2.Variable influence of NCP vs Sea-Air Flux – Patch 1: net autotrophic, NCP dominates; sea-air CO 2 flux has minor influence – Patch 3: trophic status looks neutral but depends on external sources of DIC; sea-air CO 2 flux may be dominant over time 3.Method – Ventilation calculation critical for determining NCP? – Method needs testing / refining for a lagrangian /sub- mesoscale framework

19. Next steps Consider sub-mesoscale physics to calculate ventilation fluxes Compare results with DOC, C 14 PP, O 18 R, N-flux estimates Look at heterotrophic dynamics (diurnal variability in grazing?)

20. Acknowledgements: UK-SOLAS ICON team, National Marine Facilities staff, Captain and crew of RRS Discovery. Funding: UK Natural Environment Research Council (NERC). Satellite images provided by NEODAAS, UK. Thank you!

21. B. Sea-air CO 2 fluxes Units on time plots legend!!!

22. Nutrients