1 / 18

The Earth’s Carbon Cycle

The Earth’s Carbon Cycle. Louisa Bradtmiller. Carbon Reservoirs. Size matters. How much carbon a reservoir can exchange with other reservoirs depends on Size Rate of exchange So, if we’re interested in atmospheric CO 2 , there are a few things to keep in mind. Size matters.

ruggiero-pender
Télécharger la présentation

The Earth’s 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. The Earth’s Carbon Cycle Louisa Bradtmiller

  2. Carbon Reservoirs

  3. Size matters • How much carbon a reservoir can exchange with other reservoirs depends on • Size • Rate of exchange • So, if we’re interested in atmospheric CO2, there are a few things to keep in mind

  4. Size matters • Seems like sediments would be the most likely regulator of atm. CO2, right? • But, they recycle verrrrrrrrry slooooowly • On tectonic timescales, though, they can control climate to some extent • Increased volcanism, seafloor spreading 100Ma • Increased weathering due to Himalayas

  5. Size matters • When our cars/factories emit carbon, it goes into the atmosphere • 5.4 GtC/yr from fossil fuel burning • 1 GtC/yr from deforestation • BUT not all of it stays there! • Approx. 55% stays in the atm. 30% goes into the ocean, and the rest (15%) goes to “greening” (we think).

  6. Atmosphere • We know how much goes into the atmosphere, because we can measure CO2 and CH4 levels. • We know where it comes from, because each source has a different isotopic signature • Fossil fuels are “dead carbon”, -2‰ 13C • Plants average -23‰

  7. Terrestrial Biosphere • Plants take up CO2 during photosynthesis, give it off during respiration (ie. burning, decay) • So, as long as they’re alive (or in early stages of decay) they store carbon • Plants take up 12C preferentially, giving them negative 13C values

  8. Terrestrial Biosphere • How can trees take up MORE carbon? • “Greening” involves the stimulation of increased photosynthesis via increased CO2 levels in the atm. Verified in greenhouse experiments • Another possibility is that anthropogenic N helps to fertilize plants

  9. If you haven’t seen this by now…..

  10. Ocean Carbon • Remember, there are 2 reservoirs: • Surface (upper 100 meters) • Deep (everything else) • Only the surface really “communicates” with the atmosphere- they are in equilibrium • So, is that where the carbon goes?

  11. Ocean Carbon • NOPE. The surface ocean is too small to accommodate that much C, and exchanges too quickly (it would put it right back in the atm. In a few years) • So, it must be going into the deep ocean (thus the conveyor picture)

  12. How I learned to stop worrying and love the bomb • The deep ocean “overturns” on a timescale of about 1500 years. This is long enough to store some serious C • How do we know that, anyway? • Bomb 14C- nuclear tests in the 50’s and 60’s put tons if it into the Atm. Folks (esp. Wally) watched how it was incorporated into the deep ocean

  13. Ocean carbon “pumps” • 3 types: • Solubility • organic, or soft tissue • Carbonate, or inorganic • Solubility refers to the fact that gases dissolve more easily in cold water • So, a colder ocean holds more CO2

  14. Organic Pump

  15. Carbonate pump CO2(gas) CO2 + H2O  H2CO3 H2CO3 H++ HCO3- HCO3- H++ CO32- TCO2 H2O+ CO2 + CO32-2 HCO3-

  16. Carbonate pump • In addition, many organisms make CaCO3 shells. • The solubility of these shells on the seafloor is determined by the concentration of CO32- • So, shells are preserved in shallow water, but not below the lysocline

  17. Carbonate pump • The depth of the lysocline can change with time • Easy to remember: CO2 ~ 1/CO32- • So, during a glacial, there is low CO2 and you preserve more carbonate • Or, the lysocline deepens

  18. Final thoughts • The ocean must be the regulator of modern (glacial-interglacial) carbon changes- it’s the only reservoir that is big enough and exchanges on an appropriate timescale

More Related