Carbon Fluxes, Stores, and Human Impacts
Carbon fluxes, which are measured in Petagrams (Pg) or Gigatonnes (Gt) of carbon per year, occur over various time and spatial scales. The largest fluxes typically occur between the ocean and atmosphere or between land and atmosphere, involving processes like photosynthesis and respiration.
Highlight: While processes like photosynthesis, respiration, combustion, and decomposition can transfer carbon in minutes, hours, or days, carbon sequestration in sedimentary rocks or the ocean can take millennia.
Sedimentary rocks, such as limestone, contain the vast majority (99.9%) of Earth's carbon. These rocks form through two primary processes: the compression of dead organic matter covered by silt and mud over many years, resulting in shale, and the lithification of dead marine organisms at the ocean bottom over millions of years, forming rocks like limestone.
Fossil fuels, while containing only 0.004% of Earth's carbon, play a significant role in the carbon cycle due to human exploitation. They form when organic material is deposited and accumulates faster than it can decay, eventually transforming into oil, natural gas, and coal.
Example: Chemical weathering is a geological process that releases carbon into the atmosphere. Atmospheric carbon reacts with water vapor to create weak carbonic acid, which, during condensation, forms acid rain that dissolves calcium carbonate in rocks.
Outgassing, particularly through volcanic eruptions, is another natural process that releases stored carbon into the atmosphere. Combustion, both natural (e.g., wildfires) and human-induced (e.g., burning fossil fuels), rapidly transfers carbon from biomass or fossil stores to the atmosphere.
Vocabulary: The fast carbon cycle refers to the relatively rapid movement of carbon through the biosphere, atmosphere, and upper ocean, typically occurring over days to decades.
The ocean's role in carbon sequestration is crucial and involves three interconnected systems known as pumps: the biological pump, the carbonate pump, and the physical pump. These processes move carbon between the atmosphere, surface water, and deep ocean, playing a vital role in regulating atmospheric CO2 levels and global climate.
Definition: Carbon capture and storage refers to the process of capturing CO2 emissions from industrial processes or power generation and storing them long-term, typically underground, to mitigate climate change.
Understanding these complex interactions and processes within the carbon cycle is essential for assessing and addressing the impacts of human activities on global carbon balance and climate change.
