Source: Land Model Development Team | GFDL | NOAA
The Earth system contains a fixed amount of carbon that moves among reservoirs in the solid earth, oceans, atmosphere and living organisms.
This carbon cycle carries energy in chemical bonds and is part of a series of biogeochemical cycles (i.e., nitrogen, water, carbon, oxygen and phosphorus), which are driven by energy from within the Earth and from the Sun.
Besides winds and ocean currents, the carbon cycle is the main process tying the atmosphere and the oceans together. Carbon cycles from one to the other continually and is hugely important to climate and climate change.