Oceanic carbon cycle

The oceanic carbon cycle (or marine carbon cycle) is composed of processes that exchange carbon between various pools within the ocean as well as between the atmosphere, Earth interior, and the seafloor. The carbon cycle is a result of many interacting forces across multiple time and space scales that circulates carbon around the planet, ensuring that carbon is available globally. The Oceanic carbon cycle is a central process to the global carbon cycle and contains both inorganic carbon (carbon not associated with a living thing, such as carbon dioxide) and organic carbon (carbon that is, or has been, incorporated into a living thing). Part of the marine carbon cycle transforms carbon between non-living and living matter.

Three main processes (or pumps) that make up the marine carbon cycle bring atmospheric carbon dioxide (CO₂) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon.^[1][2] The speciation^{[clarification needed]} of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans.

Earth's plants and algae (primary producers) are responsible for the largest annual carbon fluxes. Although the amount of carbon stored in marine biota (~3 Gt C) is very small compared with terrestrial vegetation (~610 GtC), the amount of carbon exchanged (the flux) by these groups is nearly equal – about 50 GtC each.^[1] Marine organisms link the carbon and oxygen cycles through processes such as photosynthesis.^[1] The marine carbon cycle is also biologically tied to the nitrogen and phosphorus cycles by a near-constant stoichiometric ratio C:N:P of 106:16:1, also known as the Redfield Ketchum Richards (RKR) ratio,^[3] which states that organisms tend to take up nitrogen and phosphorus incorporating new organic carbon. Likewise, organic matter decomposed by bacteria releases phosphorus and nitrogen.

Based on the publications of NASA, World Meteorological Association, IPCC, and International Council for the Exploration of the Sea, as well as scientists from NOAA, Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, CSIRO, and Oak Ridge National Laboratory, the human impacts on the marine carbon cycle are significant.^[4][5][6][7] Before the Industrial Revolution, the ocean was a net source of CO₂ to the atmosphere whereas now the majority of the carbon that enters the ocean comes from atmospheric carbon dioxide (CO₂).^[8] The burning of fossil fuels and production of cement have changed the balance of carbon dioxide between the atmosphere and oceans,^[6] causing acidification of the oceans.^[8][9] Climate change, a result of excess CO₂ in the atmosphere, has increased the temperature of the ocean and atmosphere (global warming).^[10] The slowed rate of global warming occurring from 2000–2010^[11] may be attributed to an observed increase in upper ocean heat content.^[12][13]

Part of a series on the
Carbon cycle
By regions Terrestrial Marine Atmospheric Deep carbon Soil Permafrost Boreal forest Geochemistry
Carbon dioxide In the atmosphere Ocean acidification Removal Satellite measurements
Forms of carbon Total carbon (TC) Total organic carbon (TOC) Total inorganic carbon (TIC) Dissolved organic carbon (DOC) Dissolved inorganic carbon (DIC) Particulate organic carbon (POC) Particulate inorganic carbon (PIC) Primary production marine Black carbon Blue carbon Kerogen
Metabolic pathways Photosynthesis Chemosynthesis Calvin cycle Reverse Krebs cycle Carbon fixation C3 C4
Carbon respiration Ecosystem respiration Net ecosystem production Photorespiration Soil respiration
Carbon pumps Biological pump Martin curve Solubility pump Lipid pump Marine snow Microbial loop Viral shunt Jelly pump Whale pump Continental shelf pump
Carbon sequestration Carbon sink Soil carbon storage Marine sediment pelagic sediment
Methane Atmospheric methane Methanogenesis Methane emissions Arctic Wetland Aerobic production Clathrate gun hypothesis Carbon dioxide clathrate
Biogeochemical Marine cycles Nutrient cycle Carbonate–silicate cycle Carbonate compensation depth Great Calcite Belt Redfield ratio
Other Climate reconstruction proxies Carbon-to-nitrogen ratio Deep biosphere Deep Carbon Observatory Global Carbon Project Carbon capture and storage Carbon cycle re-balancing Territorialisation of carbon governance Total Carbon Column Observing Network C4MIP CO2SYS
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