SOLAS/OCCC Southern Ocean Gas Exchange Experiment (a.k.a. GasEx III )

1. SOLAS/OCCC Southern Ocean Gas Exchange Experiment (a.k.a. GasEx III) Ocean Science Meeting 2006 David Ho and Dick Feely With help from their friends: Sabine, Wanninkhof, and McGillis

2. Outline Why do we care about gas exchange What have we learned so far GasEx I (1998) - North Atlantic GasEx II (2001) - Equatorial Pacific Other experiments Gas Ex III (Southern Ocean, 2008) Why Where What How

3. The Global Carbon Cycle 5 Atmospheric Pool 720 R 60 120 GPP Land Plants 560 60 2 Atm. Exchange 105 107 Rivers 0.4 Soils 1500 Net Veg. Destruction 38,000 Ocean Burial 0.2 Pools = 1015g C, fluxes = 1015g C yr-1 After Schlesinger (1991)

4. Global Ocean Carbon Dioxide

6. Basic flux equation

7. Estimates of ocean CO2 uptake using different gas exchange-wind speed relationships After Feely et al., 2001

8. Gas Transfer Velocity and CO2 Fluxes Feely et al., 2001

9. Previous US-led GasEx studies…What have we learned? NOAA Ship RONALD H. BROWN GasEx I (1998) - North Atlantic GasEx II (2001) - Equatorial Pacific

10. GasEx I (1998)

11. Highlights of GasEx I (1998) • Show that meteorological techniques for CO2 and DMS can work in the natural environment: • Direct Correlation • Profile Method • Reconcile with dual deliberate tracers 3He/SF6 • Determine changes in water column biogeochemical parameters in an anti cyclonic eddy with a large phytoplankton bloom and response to wind forcing. • Study surface concentrations, and saturation anomalies, of methyl bromide and other halogenated gases.

13. GasEx II (2001)

14. Highlights of GasEx II (2001) • Show that meteorological techniques for CO2 and DMS work in the natural environment as in 1998 using direct Correlation and Profile-Flux Methods. • Reconcile with mass balance of TCO2. • Determine diurnal changes in biogeochemistry of carbon dioxide and air-sea gas exchange rates. • Intensive measurements of biogeochemical and physical processes in the lower atmosphere and surface mixed layer. • Studies included surfactant concentrations, surface wave roughness, and surface infrared imagery.

16. Other Studies 3He/SF6 Experiments Coastal Ocean North Sea Georges Bank Florida Shelf Open Ocean Equatorial Pacific (IRONEX II) Southern Ocean (SOFeX) Sub-Antarctic Ocean (SAGE) DMS fluxes via eddy correlation Eastern Equatorial Pacific Sargasso Sea

18. DMS transfer velocities Measured with EC From B. Huebert

19. An important next step…Gas Exchange in the Southern Ocean

20. Why Southern Ocean • What are the gas transfer velocities at high winds? • What is the effect of fetch on the gas transfer? • How do other non-direct wind effects (whitecaps, possibly surfactants) influence gas transfer? • How do changing pCO2 and DMS levels affect the air-sea CO2 and DMS flux, respectively in the same locale? • Are there better predictors of gas exchange in the SO than wind? • What is the near surface horizontal and vertical variability in turbulence, pCO2, DMS and other relevant biochemical and physical parameters? • Do the different disparate estimates of fluxes agree, and if not why? • With the results from GasEx III can we reconcile the current discrepancy between model based CO2 flux estimates and observation based estimates?

21. From US SOLAS Science Implementation Plan

22. The study location should capture the germane aspects of the Southern Ocean forcing and biogeochemistry while providing a suitable environment to perform the study Where and When • Possible locations: • South Atlantic, stage out of Punta Arenas. • Southwest Pacific off New Zealand, stage out of Wellington/Christchurch. • For accurate direct flux measurements a ∆pCO2 of - 40 µatm or greater are desired. The South Atlantic has a greater ∆pCO2 than the South Pacific. However, winds and fetch are lower in the Atlantic sector. • High winds with long fetch, conductive for large swells, are desired for this experiment. The South Pacific sector has climatological ∆pCO2-20 to -40 µatm with high wind speeds and also a large range of winds speeds during the summertime with 2 - 4 day storms punctuated by more quiet periods. • Timing: • Austral summer (December through February) • Low pCO2 and weather conditions conductive for this challenging study. • Shallow mixed layer (30 - 70 m), which will facilitate studies using mass balance techniques to determine fluxes.

23. Projects envisioned A. Characterization of the biogeochemistry and physics of the study area • Waterside - surveys of the study area (100 - 1000 km2) • 4 to 8 CTDs per day (mixed layer + upper thermocline) with T, S, O2, Chl, transmissometer, and L-ADCP, O2 discrete; Chl discrete; DOM, POM, DIC, pCO2, pH, TAlk, DMS, DMS precursors, SF6, 3He • Surface intake continuous TSG augmented with Chl, O2, high response pCO2, DIC, pH, TAlk and DMS • Hull mounted ADCP • Airside • Balloons 4-8 time a day for T, humidity, O3 B. Fluxes • Airside • Meteorological packages: sonic anemometry with motion correction • Direct flux from ship: Heat, momentum, water vapor, CO2 (multiple), DMS (multiple) • Mass balance: CO2, DMS • Waterside • Carbon-mass balance • 3He/SF6 • Gas proxy studies (e.g. IR)

24. Projects envisioned (cont.) C. Surface boundary layer studies (air and water) • Multi-sensor surface and sub surface floats for near surface Lagrangian studies • Floating buoys for near-surface meteorology, fluxes • Profiling floats (mixed layer and beyond) • Surface wave field characterization (IR, laser) • Validation/up scaling of ship based anemometer with satellite remote sensing (scatterometry/IR) • Marine air boundary layer characterization with an upper air sounder D. New instrument deployment opportunities of relevance for gas exchange • Autonomous vehicles • Gas sensors • Near surface turbulence sensors • Ship based remote sensing • Water mass following floats E. Perturbation studies • Iron fertilization

25. Infrastructure • For the study, we envision using 2 ships: • One for the flux studies, whichrequires the ship to remain headed into the wind for most of the time • One for the surveys and characterization studies • 1st ship • NOAA has requested the RONALD H. BROWN for GasEx III • 2nd ship? • UNOLS • International collaboration • Other studies planned in the area: • NOAA ship RONALD H. BROWN will perform STRATUS/VOCALS off Chile • NOAA has a request for P18 (110 W). • UNOLS has requests for DIMES and Indian Ocean work.

26. Hi David, Thanks for the offer of participation in the S. Ocean GASEX. The timing of the experiment sounds good, as we were looking towards the next NZ SOLAS experiment around late 2007/early 2008. We’re interested in the experiment from a number of different perspectives and would look to collaborating with you and other US scientists in the areas of:- pCO2 and carbonate system measurements, including SAMI-CO2 Trace gas gradients (N2O, CH4, CO, DMS) REA Flux measurements (DMS, hydrocarbons) TV parameterisation (SF6/3He) Radar Sea state/wave measurements and currents Diffusion and exchange (SF6 and SCAMP/TRAMP Microstructure profilers) The Tangaroa is a potential 2nd vessel, but is already committed in Jan-March 2008 to IPY work. However, if you’re considering an iron-addition bloom experiment to kick up gas gradients then spring (late 2007) may be a better time, to maximise the chances of a biological response. From a regional perspective it may be best to get south of the ACC to ensure you have enough silicate for a diatom response. Phil will attend the meeting, but please keep us informed. Cheers Cliff