The Carbon Cycle
The carbon cycle is the movement of carbon between the four major carbon reservoirs interconnected by pathways of exchange.
- The atmosphere.
- The terrestrial biosphere.
- The oceans.
- The sediments, including fossil fuels.
The annual movements of carbon between reservoirs occur because of various chemical, physical, geological, and biological processes.
The ocean contains the largest active pool of carbon near the surface of the Earth. The deep ocean part of the carbon pool does not rapidly exchange with the atmosphere.
The global carbon budget is the balance of the exchanges (incomes and losses) of carbon between the various carbon reservoirs or between one specific loop (e.g., atmosphere ? biosphere) of the carbon cycle.
The black numbers indicate how much carbon is stored in various reservoirs, in billions of tons ("GtC" stands for GigaTons of Carbon and figures are circa 2004). The purple numbers indicate how much carbon moves between reservoirs each year. The sediments do not include the ~70 million GtC of carbonate rock and kerogen.