1 / 27

Ocean Carbon Cycle

Ocean Carbon Cycle. Figure credit US-OCB Program. Why study ocean carbon cycle?. CO 2 is an important greenhouse gas Ocean is a major sink of fossil fuel CO 2 Impacts on ocean chemistry. Rising atmospheric CO 2. SIO CO 2 program. Polar ice core data. Instrumental record.

rowa
Download Presentation

Ocean Carbon Cycle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Ocean Carbon Cycle Figure credit US-OCB Program

  2. Why study ocean carbon cycle? • CO2 is an important greenhouse gas • Ocean is a major sink of fossil fuel CO2 • Impacts on ocean chemistry

  3. Rising atmospheric CO2 SIO CO2 program Polar ice core data Instrumental record

  4. Global average ~ 1.2 TC/year/person

  5. Units for atmospheric CO2 • What do we mean by 390 ppmv? • About 0.039% of all gas molecules in the atmosphere is CO2 • CO2is a minor component of the atmospheric gases

  6. Current atmospheric CO2 is about 390 ppmv, which is equivalent of 780 GTC. Simple rule of thumb

  7. Unit matters • 1 molC = 12 gC = 44 gCO2 • 1 gC = 3.7 gCO2 • molC and gC are most frequently used in scientific literature • gCO2is also used in media, etc. • Watch out for different units!

  8. Global carbon inventory estimates • Atmosphere : 780 GTC • CO2 gas • Land biosphere : 2,000 GTC • Organic matter in forestand soils • Oceans : 38,000 GTC • Dissolved Inorganic Carbon (DIC) = CO2 gas dissolved in the seawater • Geological reservoirs • Seafloor sediment : 150 GTC • Oilreservoir : 500 GTC • Coal reservoir : 5,000 GTC

  9. Order of magnitude • 1 metric ton of C (TC) = 106gC • In 2009, US per capita carbon emission is 4.6 TC • Global CO2 emission in 2008 is about 9 GTC • 1 giga ton of C (GTC) • 1GTC = 109TC = 1015gC = 1 PgC • 1PgC = 1015gC x (1molC/12gC) = 8.3 x 1013molC 100 103 106 109 1012 1015 G k T M P kilo mega giga tera peta

  10. Concept test • Company A sells a product that reduces carbon emission at a cost of $10/TCO2 • Company B sells similar product ata cost of $20/TC • Which company is offering more cost-effective product?

  11. Concept test • If we consume entire oil reservoir, 500 GTC, how many ppmv increase do we expect in the atmosphere? • (case 1) No absorption into the ocean and/or land • (case 2) 50% absorption • (case 3) 75% absorption

  12. Emission due to human activities • DOE: Carbon Dioxide Information Analysis Center

  13. Oceans Biosphere CO2 changes in the last 50 yr

  14. The Carbon sinks • CO2 emission due to human activity • About 9 GTC/year • Time rate of increase in atmospheric CO2 • Late 2000s • Observed increase is about 4 GTC/year • Only about 45% of CO2 emitted by the human activity is remaining in the atmosphere • Where has the rest of CO2 gone?

  15. Land and ocean carbon sinks • Land biosphere • Carbon molecule is stored in trees, plants and soils • Ocean CO2 uptake • Absorption of CO2into the seawater • The carbon cycle has a stabilizing mechanism, mediating the growth of atmospheric CO2 by absorption into the land and oceans

  16. Photosynthesis and respiration • Solar energy + CO2 + H2O  Sugar + O2 • Most of energy stored in sugar is released by respiration when the biomass is consumed by animals, bacteria and people • If there is a net surplus in biomass production, biosphere can become a carbon sink

  17. Carbon uptake by the land biosphere • (Land uptake) = (Photosynthesis) – (Respiration) • Photosynthesis • Water, nutrients, sunlight • Respiration • Decomposition of organic matter • Organic matter  CO2 • Episodic events: ex. forest fires

  18. Air-sea gas transfer • Driven by turbulence at the air-sea interface • What controls the turbulent motion? Emerson and Hedges (2010)

  19. Gas transfer coefficient: G [ms-1] • Measures the strength of the air-sea gas transfer

  20. Modeling air-sea gas transfer • Sea-to-air gas flux [mol m-2 s-1] • Measures exchange of gas molecules per unit area and per unit time • Proportional to the degree of saturation Henry’s law coefficient

  21. Chemical reactions with the seawater • A series of reactions CO2 + H2O H2CO3 (carbonic acid) H2CO3 H+ + HCO3- (bicarbonate ion) HCO3-H+ + CO32- (carbonate ion) Textbook chapter 6, page 180-183

  22. Carbonate chemistry • DIC = (Dissolved Inorganic Carbon) = [CO2] + [H2CO3]+ [HCO3-]+ [CO32-] • DIC is a conserved quantity with respect to the carbonate chemistry

  23. Buffer (Revelle) factor • Fractional changes in pCO2 is related to that of DIC with a constant factor, B. • Buffer (Revelle) factor is about 10 for the modern oceans • 10% increase in pCO2 leads to 1% increase in DIC

  24. Concept test • Since industrial revolution, atmospheric pCO2 has increased from 280 to 390 ppmv. • How accurate do we need to measure DIC in order to detect the influence of rising CO2on the surface ocean DIC concentration?

  25. A little more challenging test • Let’s assume that we consume entire oil reservoir, 500 GTC, and half of coal reservoir, 2500 GTC. • If this carbon remains in the atmosphere, what would be the resulting pCO2? • What happens if we allow the entire ocean carbon reservior to respond to the rising CO2?

More Related