1. Manfredi Manizza mmanizza@ucsd.edu Scripps Institution of Oceanography University of California - San Diego Understanding the Role of Sea-Ice in the Southern Ocean CO 2 sink

2. Outline 2) Sea-Ice & Ocean physics  C-Cycle 5) Questions for future work 1) Intro – SO C-Cycle : BGC Processes & Sea-ice 3) Sea-Ice & Iron  C-Cycle 4) Sea-Ice & Air-sea gas exchange  C-Cycle

3. Modified from Vancoppenolle et al. (2013) Life in a (fizzy) freezer N2ON2O Southern Ocean Food Web 1)Open Water 2)Marginal Ice Zone 3)Ice-covered zone 3 2 1 CO 2

4. Southern Ocean Carbon Cycle Ito et al. (2010) (PgC yr -1 ) (From Princeton U.)

5. Different trajectories of Polar Carbon Sinks - SO Le Quéré et al.( 2007) Toggweiler & Russell (2008) Wind dominant driver for CO 2 uptake

6. Different trajectories of Polar Carbon Sinks - SO RECCAP, Lenton et al., 2013 OBSERVATIONS Air-sea CO 2 fluxes out in Le Quéré et al.( 2007)

7. Antarctic Sea-ice : Current State King (2014) Less Sea-Ice More Sea-Ice 1979 - 2012 Fractional Ice cover decade -1

8. Two Poles, Two Stories… AR5, WG4, CRYOSPHERE

9. Sea-Ice control on SO C-Cycle DIRECT CONTROL : 1)Air-sea gas exchange  Areas of CO 2 Uptake 2)Irradiance & PP  C-Biological Pump INDIRECT CONTROL : 1)Deep-water formation  CO 2 sequestration 2)Freshwater/Salt  Stratification & Mixing

10. Sea- Ice & Ocean Physics

11. Antarctic Sea-ice & AABW Formation

12. Antarctic Sea-ice : Current State King (2014) Less Sea-Ice More Sea-Ice 1979 - 2012 Fractional Ice cover decade -1

13. Sea- Ice & Iron

14. From bigshouth.be Iron Cycle & Sea ice in the Southern Ocean

15. Iron & sea ice in the Southern Ocean Fe included in the sea-ice model in an OCC model Fe release from sea-ice into seawater Fe uptake by sea-ice from seawater Wang et al. (2014)

16. Iron & sea ice in the Southern Ocean Diatoms Small Phytoplankton Wang et al. (2014)

17. Sea- Ice & Air-Sea Gas exchange

18. Just a Simple Lid ? Flux = α K (ΔC) (1- γ) γ ΔC = air-sea gas gradient α = solubility factor K = gas transfer velocity Loose et al., 2014

19. Moving forward K = gas transfer velocity MODEL INPUT PARAMETERS : 1)Wind Speed 2)Air-temperature 3)Sea-Ice velocity 4)Sea-Ice concentration MECHANSIMS TO MODEL OGCM + C-CYLE MODEL OF POLAR OCEANS 1)Buoyancy/Stratification 2)Sea-Ice/Water Shear 3)Gravity Waves/ice floes (Loose et al., 2014)

20. Still a long way to go… Rysgaard et al. (2011) 1)Brine & CO 2 rejection: Deep water formation process and CO 2 uptake. Two Missing Processes : 2) Sea-ice Decay & ALK release : Enhances CO 2 uptake at sea-ice margin during summer melting

21. CONCLUSIONS & FUTURE DIRECTIONS Sea-Ice can controls Southern Ocean CO 2 uptake with multiple processes (physics, chemistry, and biology) Where/when/how do we measure in the ocean bgc properties that help to understand processes and variabilty based on the use of multiple tools (in-situ, argo floats, satellites, elephant seals, etc.) ? Best way to integrate Obs. and Models to understand how changes in sea-ice will affect CO 2 uptake in the SO ?