radiocarbon cycle

Production and recycling of the radioisotope carbon-14 (14C). The radioisotope occurs when a neutron flux, caused by cosmic radiation bombarding the upper atmosphere, reacts efficiently with nitrogen present. Carbon-14 intake by living organisms eventually returns to the atmosphere when dead vegetation or animal flesh decomposes, except when it is locked in preserved organic artefacts and remains. Radioactive decay occurs, forming the basis of the radiocarbon dating method.

Initially the concentration of carbon-14 is nonuniform (levels being higher over polar regions where the Earth's magnetic field is least effective in deflecting cosmic radiation) but air currents at about 10 km/6 mi soon redistribute the newly formed carbon-14 as part of carbon dioxide gas. Around 7.5 kg/16 lb of carbon-14 is added to the Earth's carbon reservoir each year and distributed throughout the oceans, the biosphere, and the atmosphere, although variations in the magnetic field and sunspot activity can alter the intensity of cosmic radiation, affecting carbon-14 production.