NOAA operates the largest ship of opportunity (SOOP) effort for surface CO2 observations in the world. The objective of the ocean acidification (OA) monitoring effort in the coastal ocean on NOAA fisheries ships Gordon Gunter and Henry B. Bigelow is to obtain data for a data-based ocean acidification product suite for the East Coast and Gulf Coast. The ship of opportunity (SOOP) in support of OA monitoring (SOOP-OA) is in direct response to the needs expressed in the NOAA OA strategic plan, national and international program documentation, to understand how the rates and magnitude of acidification will vary across time and space, as a consequence of local and regional geochemical, hydrological, and biological variability and trends. The core of understanding rests upon monitoring the carbon system and related physical and biogeochemical parameters that are used to characterize the state of the coastal ocean in the project area.
The NOAA fisheries ships Gunter and Bigelow provide regular cruise tracks used in stock assessments such that over time correlations and causality can be obtained between OA and fisheries interests. The repeatability also provides good snapshots of change. As there are robust correlations between surface CO2 levels and remotely sensed parameters, these data are critical for the mapping of OA parameters. The development of algorithms to perform this mapping is done from support measurements on the SOOP-OA, other SOOP data under our purview, and from the dedicated research cruises.
Dedicated research cruises are used to obtain subsurface measurements and a comprehensive suite of biogeochemical observations to gain a process level understanding of OA. OAP provides funds to carry out the Gulf of Mexico and East Coast Carbon (GOMECC) research cruises every 5 years. These cruises provide a data set of unprecedented quality of physical and chemical coastal ocean parameters that is used both for improved spatial understanding of OA and also to provide a general understanding of changing patterns over time by comparison with previous cruises. The monitoring component is an essential part of the OAP, providing a long-term assessment of changes of biogeochemistry and ecology in response to increasing CO2 atmospheric levels and large-scale changes in coastal dynamics.
The climate quality data from the research cruises provide an important link to the Global Ocean Acidification Network (GOAN) effort, and contribute to a long-term record of dynamics and processes controlling OA on the coastal shelves. The data are used for validation measurements of autonomous assets, applying the data for algorithm development utilizing remotely sensed signals that are used to characterize saturation states, and to project the future state of ocean acidification in the project area. The GOMECC research cruises have now been divided into two cruises, one focused on the east coast, the “East Coast Ocean Acidification” (ECOA) cruise and the other covering the Gulf of Mexico, the “Gulf of Mexico Ecosystems and Carbon Cycle” (GOMECC) cruise.
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.
This project contributes to the NOAA objective to provide accurate and reliable data from sustained and integrated earth observing systems through research, development, deployment, and operation of systems to collect detailed carbonate chemistry measurements as a part of a hydrographic research cruises along the west coast. The NOAA Ocean Acidification Monitoring Program along North American coastlines (Atlantic, Pacific, Gulf, and Alaskan) and in the global open ocean will focus on mapping and monitoring the distribution of key indicators of ocean acidification including carbon dioxide, pH, and carbonate mineral saturation states. The overarching goal of the program is to determine the trends in ocean acidification (OA) and to provide concrete information that can be used to address acidification issues. The detailed hydrographic research cruises that are planned to be conducted every four years along our coasts are essential for providing high-quality intercalibration data across the full suite of OA observing assets in coastal waters, including well-proven technologies such as the MAPCO2 moored CO2 system and underway pCO2 systems on ships-of-opportunity as well as developing technologies such as wave gliders and sensors for additional carbon parameters.
The hydrographic cruise measurements facilitate the overall monitoring effort's ability to address the near-term performance measure of quantifying aragonite saturation state in the areas studied to within 0.2. In addition, the recurring coast-wide cruises allow us a critical opportunity to assess OA conditions along the West Coast in a synoptic fashion. Cruise-based observations have provided critical information for model validation that is facilitating the improvement of next-generation physical-biogeochemical models projecting OA conditions into the past and the future.
PMEL's surface observational network, consisting of the complementary moorings and underway observations, is designed to quantify the temporal and spatial scales of variability of carbon species, pH, and aragonite saturation in surface waters. To assess spatial dynamics in OA and evaluate the synergistic effects of coastal processes along the coasts and in the open ocean, we will leverage our Ship of Opportunity Program (SOOP) infrastructure along the U.S. west coast. Underway observations have been enhanced by the collection and analysis of discrete DIC and TA samples beginning in FY 2010.
The primary objectives of our underway OA FY 2015–2017 sustained investment work plan are to maintain existing underway observations on NOAA Ships Oscar Dyson and Bell Shimada with autonomous pCO2, pH, and ancillary sensors that cover the continental shelf regions of Alaska, Washington, Oregon, and California. We plan to work with Dr. Rik Wanninkhof''s group at AOML to ensure that the underway OA system on NOAA Ship Ronald Brown is working well for the FY2016 West Coast Ocean Acidification cruise. In addition to making ongoing observations from existing OAP-funded CO2/pH SOOP platforms, during this funding period we are placing a major emphasis on finalizing QC on backlogged underway pH and DO data, distributing the final data to CDIAC and NODC data archives, and data synthesis and publication efforts. These efforts are being undertaken in conjunction with other members of the PMEL Carbon Group, the PMEL Science Data Integration Group, our AOML sister group, and Dr. Todd Martz at Scripps Institution of Oceanography. Finally, under the OAP SI FY15-17 work plan, we will continue to maintain the pH and O2 sensors that are presently on the container ship Cap Blanche and contribute to the trans-Pacific decadal time-series.