The Repeat Hydrography program began its at-sea operations in 2003, in support of the objectives of the US Carbon Cycle Program and US CLIVAR. This site provides background on the scientific rationale and scope of the integrated approach to a global observational program for carbon, hydrographic and tracer measurements. Working documents are included on implementation and timing of sections, core measurements, and data management protocol. This site provides links to the data sets collected in the Repeat Hydrography Program.