lecture+17+Global

Oceans can be evaluated using changes in atmospheric

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Oceans can be evaluated using changes in atmospheric oxygen, in comparison to carbon dioxide.
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Where is the rest of the Carbon Dioxide Going? Oceans can be evaluated using changes in atmospheric oxygen, in comparison to carbon dioxide. Also, isotopes of carbon are useful. Additionally, C isotopes can be used to evaluate biotic (deforestation) and fossil fuel sources of carbon dioxide.
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Carbon Isotopes There are three important isotopes of C 12 C, 13 C, and 14 C - and they are useful because they tell different stories. 12 C is the abundant one 13 C is discriminated against in photosynthesis by about 2% relative to 12 C - and so fossil fuels, plants, and soils are all depleted in it. Consequently both fossil fuel combustion and deforestation dilute atmospheric 13 C. 14 C also is discriminated against in photosynthesis, by about 4%. In addition, it’s a radioisotope with a half -life of about 5700 years that’s depleted by decay – and fossil fuels contain essentially none of it. So fossil fuel combustion dilutes 14 C much more than it does 13 C, while deforestation depletes them more nearly equally
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Global Estimates Deforestation made a substantial contribution through the first half of the 20 th Century, but the source now is overwhelmingly fossil fuels. These global measurements are the best way of calculating the overall flux of carbon dioxide between the atmosphere and terrestrial biota. It’s possible to do meaningful ecosystem science on the scale of Earth and it’s important!
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Oceans can be evaluated using changes in atmospheric oxygen...

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