GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012)
Christoph HeinzeUniversity of Bergen, Geophysical Institute andBjerknes Centre for Climate ResearchProf. in Global Carbon Cycle ModellingAllegaten 70, N-5007 Bergen, NorwayPhone: +47 55 58 98 44 Fax: +47 55 58 98 83Mobile phone: +47 975 57 119 Email: [email protected]
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.”
Sarmiento&Gruber 2006 Chapter 3:
Air-sea interface, part 2
Surface CO2 air-sea flux climatology, Takahashi et al., 2009
Sea-air CO2 flux
February
August
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?
Solubility – ideal/non-ideal gases:
Black board
Sarmiento & Gruber (2006)
Solubilities of gases and sea water temperature:
Sarmiento & Gruber (2006)
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
CO2
Solubilities of gases and salinity:
Weiss, Mar.Chem., 1974
Solubility coefficients for CO2
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
Zeebe & Wolf-Gladrow 2001
The stagnant film model of air-sea gas exchange:
Sarmiento & Gruber (2006)
Jähne and Hauβecker, Annu. Rev. Fluid Mech. 1998
Flux: jc = k (Cs-Cb) =D/z (Cs-Cb)
D= Sc/ν
Sc=ν/D Schmidt numberD: diffusion coefficient for concentrationν: 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
Stagnant film model:
Black board
Sarmiento & Gruber (2006)
Overview gases and resistances in water and air phases:
Jähne and Hauβecker, Annu. Rev. Fluid Mech. 1998
Overview - stagnant film model, film replacement model, boundary layer model:
Stagnant film model:
1/k ~ Sc1
Micrometeorological boundary layer model (turbulence theory, Deacon, 1977):
1/k ~ Sc2/3
Film replacement model:
1/k ~ Sc1/2
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.
Source: Sarmiento&Gruber 2006
Source: Sarmiento&Gruber 2006
