Cosmic radiation dating
The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate.Most of the cosmic ray particles reaching the Earth are produced outside the solar system during supernova explosions.Mainly two magnetic shields, the solar magnetic field and the geomagnetic field, modulate the cosmic ray flux approaching the Earth.Both shields vary in time, and so does the cosmic radiation at Earth.Carbon-14 is continually produced in the upper atmosphere as neutrons, which are by-products of cosmic rays, and is then absorbed by nitrogen atoms.Carbon-14 atoms react with oxygen to form carbon dioxide, and carbon-14 is incorporated into the food chain when plants use carbon dioxide for photosynthesis.The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record.
Radiocarbon enters the biosphere through natural processes like eating and breathing.
Living things contain carbon-14 and carbon-12 in a ratio that is the same as in the atmosphere at the time.
When the organism dies, the ratio of carbon-14 to carbon-12 decreases, as carbon-14 decays and is no longer incorporated into the organism.
Although their production processes are very similar, their geochemical behavior in the Earth system is completely different (Fig. ) calculated with a box-diffusion carbon cycle model (4) is a better measure of the cosmic radiation, but it still contains a climate signal component due to unknown temporal changes of the carbon cycle and a memory effect of the production history.
In contrast to Be directly reflects cosmic ray intensity variations with almost no attenuation and a delay of 1–2 y.
This dating method works by measuring the ratio of different isotopes of carbon in a sample using a particle accelerator, such as the ANTARES accelerator at ANSTO. The carbon-12 isotope makes up 99% of all carbon on earth, carbon-13 accounts for almost 1%, and carbon-14 is found in trace amounts.