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: christoph.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.”

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