Collaborative Research: Understanding the Changing Global Distribution of Radiocarbon: Sampling and Analysis from GO-SHIP and Ships of Opportunity Cruises

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Radiocarbon has long been recognized as an important tracer for studies of ocean processes. The major objective of this project is to continue a systematic global resampling of the oceanic radiocarbon distribution as part of the US Global Ocean Carbon and Repeat Hydrography program, a part of the international Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP) network of sustained observations. Continued sampling of select repeat hydrography lines as well as the collection of samples from other important regions will provide the global carbon cycle community with a robust database to test ocean general circulation models. This is particularly important based on our reliance on such models to predict the consequences of increased global carbon dioxide. 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 carbon dioxide in the ocean, and to evaluate ocean general circulation model performance. The samples to be collected are focused on, but not limited to, the Indian and the Southern Oceans. The researchers will collect and analyze samples from planned repeat hydrography Atlantic cruises over the next 5 years. The total planned sampling will help provide an updated estimate of the three dimensional radiocarbon distribution for the Indian Ocean in addition to monitoring changes in the bomb-14C transient. Their repeat sampling schedule is, by design, a bit slower than for the general Repeat Hydrography program. This reduction is a compromise based on budgetary considerations, sample analysis capacity and cruise plans. They will also sample in the Southern Ocean as part of the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) effort. These samples will document the radiocarbon distribution in this poorly understood region of the ocean and provide important information about carbon flux and transport through this area.