Adrienne Sutton and Chris Sabine, NOAA Pacific Marine Environmental Laboratory
The PMEL Carbon Group has been augmenting and expanding high-frequency observations on moorings to provide valuable information for better understanding natural variability in inorganic carbon chemistry over daily to inter-annual cycles. The current NOAA Ocean Acidification Observing Network (NOA-ON) consists of 21 moorings in coral, coastal, and open ocean environments. At present, the OA mooring network includes a standardized suite of surface sensors measuring for air and seawater partial pressure of CO2 (pCO2), pH, temperature (T), salinity (S), dissolved oxygen (DO), fluorescence, and turbidity at all sites. Although OA is primarily driven by uptake of CO2 from the atmosphere, many coastal and estuarine processes that affect water chemistry and the interpretation of coastal OA are manifested in subsurface waters. Furthermore, many of the most sensitive organisms (e.g. corals, shellfish) are benthic and respond to subsurface water chemistry.
The Moored Autonomous pCO2 (MAPCO2) systems currently used on the 21 OA moorings are uniquely adapted for surface only measurements. PMEL has demonstrated these MAPCO2 systems are compatible with and comparable to ship-based underway pCO2 systems and discrete validation measurements used in the NOA-ON. However, similar standardized methods and technologies have not been evaluated for subsurface observations on the existing mooring network. Our project evaluates the best carbon system technologies to deploy in the subsurface, demonstrate the utility of these enhanced observations on the moorings, and make recommendations on how advanced technologies can be incorporated into the NOA-ON.