TRACER STUDIES OF C-14 IN THE NORDIC SEAS BY AMS MEASUREMENTS

At a time of important interest in climate, the Nordic Seas are especi ally in focus as a sink for CO2 and the further transfer to the deep w ater in the Atlantic Ocean. The relatively short time constant in this process provides possibilities to study the circulation by applicatio n of tracers. C-14 is one of the most representative isotopes in this study, and several deep sea profiles have been obtained in seven summe r cruises during the last years. For modelling studies it has been esp ecially important to repeat some GEOSECS profiles obtained 20 years ea rlier in this area. Some of the first C-14 profiles were obtained with conventional CO2 counting technique based on 100-200 l seawater. Most of the later profiles have, however, been measured with the AMS techn ique at the Arizona AMS facility, based on 0.5 l seawater. The small s amples make this technique especially preferable for sample collection on board ship and in further laboratory treatment. The precision in t he isotope ratio measurements is generally 6 parts per thousand for a counting time of 20, min per sample. Higher precision (3-5 parts per t housand) has, however been achieved with several accelerator targets.