Determining the “birthday” of e.g. microfossils, wood, leaves, bivalves or other components found in samples gathered from the seafloor requires high-precision analytical work – a challenge that the Alfred Wegener Institute’s C-14 lab has now overcome. To do so, the scientists use a method called radiocarbon dating, also known as the C-14 method.
The C-14 method involves measuring the proportion of the radioactive carbon 14C isotope (C-14) to the stable 12C isotope. Radioactive carbon is formed in the atmosphere and subsequently absorbed by all life on Earth. In living organisms, the 14C level largely remains stable, since they are in constant contact with the atmosphere. When they die, however, this exchange with the atmosphere comes to an end. The 14C content is then measured using the radioactive decay, which progresses on the basis of a specific half-life, while the stable carbon isotopes remain unchanged. In this way, measuring the isotope proportion 14C/12C can tell us how old a given sample is.
Normally an accelerator mass spectrometer is used for the 14C method – traditionally a massive machine that takes up an entire room and has to be constantly supervised by several personnel. Accordingly, in the past, samples were always sent to major labs equipped with such systems, though doing so was quite expensive. However, thanks to the evolution of the conventional accelerator mass spectrometer, for some time now much smaller units, specially designed for the 14C method, have also been available. “The high costs of external analyses are one of the reasons why the AWI now has its own 14C lab,” says Gesine Mollenhauer, a marine geochemist and head of the laboratory. To date, the AWI is the only institute in northwest Germany with a next-generation 14C accelerator mass spectrometer, which can perform analyses with even the smallest amounts of carbon; the main reason the AWI chose to invest in the new technology.