Understanding the exposure of the nation’s living marine resources such as shellfish and corals to changing ocean chemistry is a primary goal for the NOAA OAP. Repeat hydrographic surveys, ship-based surface observations, and time series stations (mooring and ship-based) in the Atlantic, Pacific, and Indian Oceans have allowed us to begin to understand the long-term changes in carbonate chemistry in response to ocean acidification. These efforts are made possible by working with many divisions and programs within NOAA, partnering with federal and state agencies, and academic and private institutions.

There are many approaches and platforms from which these observations can be made. To find out more about the various instruments currently used and being developed by NOAA ocean acidification researchers and partners explore the images below:

Monitoring demands high quality observations that allow for a comprehensive understanding of how ocean chemistry is changing in response to ocean acidification. When people typically think of ocean acidification, they think of pH. However, acidification affects several aspects of carbonate chemistry including 1) partial pressure of carbon dioxide (pCO2), 2) pH, 3) total dissolved inorganic carbon (DIC), and 4) carbonate ion availability, which can each potentially affect marine life in a different way. 

Fully understanding the carbonate system demands not only measuring temperature and salinity, but also knowledge of at least two of four measurable, carbonate chemistry parameters: pH, DIC which is the sum of all inorganic carbon (carbon dioxide (CO2), carbonic acid (H2CO3), bicarbonate ions (HCO3-2) and carbonate ions (CO3-2) in solution), total alkalinity (the buffering capacity of a liquid), and pCO2. If two of these parameters are known then the calcium carbonate saturation state can be estimated.

Our autonomous fixed and underway ocean acidification (OA) platforms build on a network of moorings which were originally designed to measure the uptake of CO2 into the ocean. More recently, pH has been added to these platforms in an effort to estimate the calcium carbonate saturation state of the waters, which can be used as an indicator for the ability of some marine organisms to produce calcium carbonate skeletons and shells. In addition, dedicated geochemical ship survey efforts are used to monitor all four parameters from water samples collected in both surface and deep water environments throughout most of the coastal U.S. Large Marine Ecosystems. Dissolved oxygen (O2), is also a common measurement offering insight into the local biogeochemical controls on carbonate chemistry dynamics. Measuring these variables offers insight into the rate of CO2 uptake into the ocean from the atmosphere, and the resulting effects on carbonate chemistry, saturation state, and the status of marine life and feedbacks on various ecosystems.

Credit: Cathy Cosca, PMEL

The map above depicts NOAA ocean acidification observing efforts currently underway in red circles. Current tracks of volunteer observing ships (VOSs) are shown by green lines. VOSs are ships travelling for commercial or non-scientific purposes that have been equipped with instruments that measure temperature, salinity and pCO2 with automated carbon dioxide analyzers as well as thermosalinographs (TSGs). These greatly enhance the area in which carbon data can be collected. The blue lines depict hydrographic research cruises dedicated to collect ocean acidification samples.