Project: RAPID: Continuation of U.S. GEOTRACES North Atlantic Section: CFC and SF6 Measurements

NSF Award Abstract:
The U.S. GEOTRACES North Atlantic campaign cruise was launched from Lisbon on the R/V/ Knorr in October, 2010. Unfortunately, in mid-course, a problem with the propulsion system developed, and the cruise had to be aborted. The Knorr went to a shipyard in Charleston, SC for repairs where scientific equipment and samples were offloaded there and shipped back to the various home institutions of the various scientists.

This project addresses the efforts of one investigator originally funded through an ARRA award to participate in the North Atlantic campaign -- to resume a set of essential observations when the field program resumes in November, 2011.

With support through a Grant for Rapid Response Research (RAPID), a research team at the Lamont-Dougherty earth Observatory will measure the CFC-11, CFC-12 and SF6 distributions along the autumn 2011 continuation of the previously aborted US GEOTRACES North Atlantic transect. They will use these data to identify the most recently ventilated cores of the North Atlantic water masses, to estimate transit times of these water masses from their source regions, and to estimate oxygen consumption rates and rates of production or decomposition of selected trace elements measured on this program using the transit time information. Such measurements are critically important to understanding how the physical processes of advection, mixing, and water mass formation affect the distributions of trace elements and isotopes in the ocean. The evolving CFC and SF6 distributions in the ocean provide strong constraints on these processes. Measurement of CFCs and SF6 on the GEOTRACES program places the GEOTRACES data in the context of large scale ventilation patterns established by CFC/SF6 measurements on these cruises.

Broader Impacts. In addition to providing information on ventilation and transit times for the GEOTRACES project, the CFC and SF6 data collected on this cruise will also expand the transient tracer data base for the North Atlantic Ocean. The data will be disseminated widely to the research community following NSF guidelines. Several CLIVAR cruises to the North Atlantic are planned for the 2010 - 2012 time period, and the GEOTRACES cruise will increase the coverage for CFCs and SF6. This database of the temporally evolving CFC and SF6 concentrations in the North Atlantic Ocean is used in studies of the role of the ocean in global climate and the global CO2 cycle. It is used to validate models of ocean circulation and to quantify the uptake and storage of anthropogenic CO2 in the ocean. Such information is critical for society to make sound decisions on policies to deal with climate change.