Modelling carbon fluxes from the land to the open ocean: a journey along inland waters, estuaries, tidal wetlands and the coastal ocean
Carbon is the primary component of life on Earth, and a major component of many minerals. Most of Earth’s carbon is stored in the lithosphere, in rocks and sediments. On land, carbon is found in the soil, water bodies and all living organisms. The ocean also stores a significant amount of carbon, mainly dissolved in the water column, and as particulate compounds in marine sediments. In the atmosphere, carbon dioxide (CO2) is the main carbon molecule, with methane (CH4) and other compounds present in small amounts. Carbon reservoirs can act as sources of carbon, releasing carbon to other reservoirs, or as sinks, absorbing it. Natural sources for the atmosphere include, e.g., volcanism, or plant respiration and decomposition, while photosynthesis, bedrock weathering and sediment burial are natural sinks. Fossil fuel combustion or land-use changes, such as deforestation and peat drainage, are examples of anthropogenic carbon sources. These anthropogenic sources have induced profound changes in atmospheric composition and climate, which in turn have altered many natural processes of the global carbon cycle. For instance, the ocean was a small natural CO2 source during pre-industrial times, while it is now a significant carbon sink for the atmosphere. These continuous exchanges of carbon between reservoirs through a variety of biogeochemical processes form the global carbon cycle which, along with the nitrogen and water cycles, plays a key role in maintaining life on Earth.
