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Geosciences LibreTexts

13.6: Climate & Carbon Cycle

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  • What is the Carbon Cycle?

    The carbon cycle can be described as the flux of carbon between the Earth’s sediments, life, the atmosphere, and the ocean. The amount of carbon present within all these systems is always the same but the amount it can be in each form can vary with time and with increased human activities.

    The Carbon Cycle: a map illustrating how carbon moved thought the environment.

    As depicted in the figure above, we can see that there are multiple natural and unnatural sources of carbon dioxide present in the atmosphere, which release carbon. Some of these natural sources include respiration of macro- and microorganisms, the decay of organic material, and fire. Burning fossil fuels is an example of an unnatural carbon dioxide source. Carbon sinks, which absorb carbon, are also present in this cycle and include photosynthesis and carbon dioxide exchange with the ocean. The ocean takes in nearly 48% of all CO2 emissions from fossil fuel burning (NASA). Data produced by NASA describes how carbon moves throughout these pools described as the Geosphere (rock), Atmosphere (gases), Biosphere (life), and the Hydrosphere (water), at a constant equilibrium that has been thrown off-balance by the amount of anthropogenic atmospheric carbon dioxide emissions. We can’t rely on the ocean as a carbon source indefinitely; we know from studies that increased carbon dioxide is harmful to marine organisms, such as corals, and oceanic circulation cycles including thermohaline circulation.

    Since the industrial revolution, humans have been burning fossil fuels and pumping more CO2 into the atmosphere leading to serious alterations to the carbon cycle. Without the burning of fossil fuels, the net amount of CO2 in the atmosphere remains the same as it moves throughout various forms. The biggest source of carbon on earth is within sediments on land and in the ocean. This means that when we extract and burn coal and fossil fuels the sediments, we are adding carbon to the atmosphere. This is different than burning wood because the carbon within trees is taken from the atmosphere and therefore a part of the carbon cycle while the carbon from these sediment sources was not. This is a problem because we are adding carbon to the atmosphere and the carbon cycle. This has serious implications for the ocean because as the atmosphere becomes more saturated with CO2, more of it dissolves into the oceans. The mixing of CO2 in the oceans leads to ocean acidification; which can have a series adverse effect on all kinds of marine life (See our section on Ocean Acidification [Add Link on LibreTexts]).

    This image shows the global carbon cycle but with a focus on the ocean. Also, note the main organisms in the ocean that help facilitate the process.

    The distribution of carbon in the ocean varies starkly between actors in the carbon cycle. This will ultimately influence the global circulation of carbon. Note the differences in the amount of carbon stored between the deep ocean, surface ocean, and sediments below.

    Diagram showing the physical, biological, and chemical processes affiliated with the Carbon Cycle.

    Multimedia - Carbon Cycle Interactive Diagram

    Use this interactive diagram to explore the various ways that carbon movies from the earth to the atmosphere, and the ocean.

    Video - Southern Ocean Carbon Sink

    Watch video this video to see the current state of our southern oceans and how the carbon cycle is being affected by climate change.

    Carbon Cycle Glossary

    Here is a link to a Carbon Cycle Glossary



    2. The Global Carbon Cycle Crash Course Video

    3. 5 Human Impacts on the Environment: Crash Course Ecology

    4. "Carbon Cycle | Science Mission Directorate." N. p., 2019. Web. 7 Mar. 2019.