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GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in Global Carbon Cycle Modelling Allegaten 70, N-5007 Bergen, Norway Phone: +47 55 58 98 44 Fax: +47 55 58 98 83 Mobile phone: +47 975 57 119 Email: christoph.heinze@gfi.uib.nochristoph.heinze@gfi.uib.no DEAR STUDENT AND COLLEAGUE: ”This presentation is for teaching/learning purposes only. Do not use any material of this presentation for any purpose outside course GEOF236, ”Chemical Oceanography”, autumn 2012, University of Bergen. Thank you for your attention.”
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Sarmiento&Gruber 2006 Chapter 3: Air-sea interface, part 2
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Surface CO 2 air-sea flux climatology, Takahashi et al., 2009 Sea-air CO 2 flux February August
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Central issue in this chapter: What controls the air-sea flux / sea-air flux of different gases? How can this flux be quantified (or predicted)? Conceptual model Flux Φ of gas across water air interface: Φ = transfer velocity ∙ concentration gradient What is the transfer velocity and on what does it depend? How to determine the concentration gradient?
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Solubility – ideal/non-ideal gases: Black board Sarmiento & Gruber (2006)
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Solubilities of gases and sea water temperature: Sarmiento & Gruber (2006)
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Broecker, W.S., and T.-H. Peng, 1982, Tracers in the Sea, ELDIGIO Press, Palisades NY, 690 pp. Solubility of gases and the sea water temperature CO 2
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Solubilities of gases and salinity: Weiss, Mar.Chem., 1974 Solubility coefficients for CO 2
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Ideal gases Source: Inorganic chemistry textbook by Christen, 1982 Ideal up to about 1%, for p less or equal 1 atm and T over 0 deg C pressure volume
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Zeebe & Wolf-Gladrow 2001
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The stagnant film model of air-sea gas exchange: Sarmiento & Gruber (2006)
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Jähne and Hauβecker, Annu. Rev. Fluid Mech. 1998 Flux: j c = k (C s -C b ) =D/z (C s -C b ) D= Sc/ ν Sc= ν /D Schmidt number D: diffusion coefficient for concentration ν: diffusion coefficient for momentum (kinematic viscosity) The stagnant film model of air-sea gas exchange: Index s for surface, index b for bulk For Ostwaldt solubility α=3
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Stagnant film model: Black board Sarmiento & Gruber (2006)
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Overview gases and resistances in water and air phases: Jähne and Hauβecker, Annu. Rev. Fluid Mech. 1998
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Overview - stagnant film model, film replacement model, boundary layer model: Stagnant film model: 1/k ~ Sc 1 Micrometeorological boundary layer model (turbulence theory, Deacon, 1977): 1/k ~ Sc 2/3 Film replacement model: 1/k ~ Sc 1/2
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Gas transfer velocity versus wind speed (for a gas with Sc≈600). Liss, P., and L. Merlivat, 1986, Air-Sea gas exchange rates: Introduction and synthesis, in: The role of air-sea exchange in geochemical cycling, P. Buat-Ménard, editor, Dordrecht, Holland, 113- 127.
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Source: Sarmiento&Gruber 2006
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