Time-series records are key to characterizing the natural variability and secular trends in the ocean carbon cycle and for determining the physical and biological mechanisms controlling the system. Year-to-year variations in physics (e.g., upwelling, winter mixing, lateral advection), bulk biological production, and ecological shifts (e.g., community structure) can drive significant changes in surface pCO₂ (and thus air-sea flux) and surface nutrient fields. The biological and chemical responses to natural perturbations (e.g., ENSO, dust deposition events) are particularly important with regard to evaluating potential climate responses and for evaluating the prognostic models used in future climate projections.

Ship-based time-series measurements are impractical for routinely measuring variability over intervals from a week to a month; they cannot be made during storms or high-sea conditions, and they are too expensive for remote locations. Instrumental advances over the past 15 years have led to autonomous moorings capable of sampling properties of chemical, biological, and physical interest with resolution as good as a minute and a duty cycle of a year or more (e.g., Chavez et al., 1999; Dickey, 2003). This work has provided a growing body of evidence that episodic phenomena are extremely important causes of variability in CO2 and related biogeochemical properties and processes. Time-series moorings are essential for documenting the temporal evolution of the ocean carbon system. These moorings, particularly when co-located with shipboard time-series programs, are also invaluable for developing and testing new chemical and biological techniques and autonomous sensors as well as serving as focal points for process studies.

The moored pCO₂ program started in 1996 as a collaborative research project between the Monterey Bay Aquarium Research Institute (MBARI) and NOAA's Pacific Marine Environmental Laboratory (PMEL). With support from the NOAA/OACES (then NOAA/OGP's Global Carbon Cycle program) and NASA/SIMBIOS programs, MBARI developed and deployed two pCO₂ systems on TAO buoys in the Equatorial Pacific (at 0°, 155°W and 2°S, 170°W). In 2002 NOAA's Global Carbon Cycle (GCC) program funded a proposal to begin transferring the pCO₂ system technology developed at MBARI to PMEL. In 2004, the moored CO₂ program was picked up by the Office of Climate Observations (OCO) as part of the ocean observing system for climate. The moored pCO₂ network is still in its infancy, but is quickly expanding into a global network of surface ocean and atmospheric CO₂ observations that will make a substantial contribution to the production of CO₂ flux maps for the global oceans. The long-term goal is to populate the network of OCEAN Sustained Interdisciplinary Timeseries Environment observation System (OceanSITES) so that CO₂ fluxes will become a standard part of the global flux mooring network. This effort has been endorsed by the OceanSITES science team. Additional information about the moored pCO₂ program can be found at: http://www.pmel.noaa.gov/co2/moorings/. Locations of the moorings are given in Figure 1.

Bermuda Testbed Mooring (64.2°W, 31.7°N) - New Deployment Site. This mooring (Figure 2) was deployed in October 22, 2005. The PMEL-built system is operating properly and typical ocean and atmospheric pCO₂ data are shown below in Figure 3. For updates, Please go to: http://www.pmel.noaa.gov/co2/moorings/btm/btm_main.htm