The major objective of this study is to collect and analyze both radiocarbon (P14PC) and stable carbon (P13PC, P12PC) isotopes during the second phase of the CLIVAR Repeat Hydrography (RH) program. The study will be focused on the Atlantic Ocean. Samples will be collected and analyzed from all of the planned RH Atlantic cruises over the next 6 years and additionally from 4 non-US repeat cruises. The total planned sampling will allow an updated estimate of the 3-D radiocarbon distribution for the Atlantic in addition to monitoring changes in the bomb-P14PC transient. Sampling for radiocarbon will continue on a repeat schedule of 15-20 years, slower than the international CLIVAR repeat sampling of once per decade.
Radiocarbon has long been recognized as an important tracer for studies of ocean processes. Data generated from this study can be used to study mixing, ventilation rates, production rates, residence times in the deep ocean, deep ocean biogeochemistry and oxygen use rates, air-sea gas exchange, thermocline ventilation rates, as a proxy for anthropogenic COB2B in the ocean, and to evaluate ocean general circulation model (OGCM) performance. The latter application is particularly important based on our reliance on such models to predict the consequences of increased global COB2B. The combined input of radiocarbon and CFCs into OGCMs provides a critically important test of the models that cannot be gained through one tracer alone.
The study includes no funding for scientific interpretation nor for student participation of any kind (with the exception of high school students as bottle washers). Consequently, the immediate broader impacts are very limited. Once the data are public and especially after they have been incorporated into large scale data products the results are expected to have important and very wide impact on both the biogeochemical and physical oceanographic fields. The data will be combined with results from all available sources and will be available to the entire global community in easy to use formats.
