The U.S. program measurements are presently divided into three levels in order of priority. Level 1 core measurements are mandatory on all cruises. The levels are also the suggested standard for international collaborators, and should be measured at the highest practical spatial resolution. The rationale for classifying a measurement as Level 1 is based on data required to directly quantify change in ocean carbon inventory, estimate anthropogenic CO2 empirically, characterize large-scale water mass ventilation rates, constrain horizontal heat, freshwater, carbon, nitrogen, and oxygen transports and/or net divergence, and provide an on-going basis for model evaluation. Level 2 measurements are highly desirable. They may be collected on coarser spacing and will be closely coordinated with the core effort. Level 3 ancillary measurements are done according to opportunity and space available. They should not significantly interfere with Level 1 or 2 efforts, and may be regional or specific to an individual cruise.
Within the U.S. a consortium of scientists typically leads each Level 1 and 2 observation type, working to integrate their measurement program within the framework of the Carbon/CLIVAR national and international program requirements.