GCOS Ocean Surface ECV
Carbon Dioxide Partial Pressure (pCO₂)

Introduction: The surface ocean partial pressure of CO₂, pCO₂, is a critical parameter of the oceanic inorganic carbon system (a) because it determines the magnitude and direction of the exchange of CO₂ between the ocean and atmosphere, and (b) because it is a good indicator for changes in the upper ocean carbon cycle. In addition, it is an oceanic parameter that can be routinely measured with high accuracy and precision. The first measurements of pCO₂ were initiated in the early 1960s, and the sampling network has grown substantially since then. However, most efforts so far have been driven by single investigators, while only recently international coordination efforts, largely led by IOCCP, have been initiated. As a result, the international network of surface pCO₂ observations is in the early stages of development.  Current network activities include: 

1. Approximately 20 operational programmes underway measuring pCO₂; approximately 12 of these programmes are doing full trans-basin sections. Nearly all of these programmes are funded by time-limited funds, and many of them are nearing the end of their funding period.
2.  Automated drift buoys (number varies; typically 5-10 operating at any given time).
3.  Surface time series stations – approximately 10 stations.
4.  International planning and coordination provided by the IOCCP.

Although this network has provided the basis for estimating the climatological air-sea fluxes of CO₂, the observations are inadequate to resolve year-to-year variations and to provide flux estimates at any resolution higher than several hundred kilometres.
 
Issues relative to the development of an integrated and operational network to meet GCOS needs are:

1. Improved technology/automation for on-board systems including careful calibration.
2.  Development of an internationally-agreed implementation strategy to identify priorities for the sustained system.
3.  Sustaining priority trans-basin programmes and development of new programmes according to implementation strategy priorities.
4.  Investigations of potential objective mapping routines and interpolation techniques including remote-sensing and model-data assimilation. Auxiliary observations that have proven to be particularly useful are sea-surface temperature, mixed layer depth, and surface chlorophyll. 

To address these issues it is proposed that IOCCP, in consultation with the OOPC, develop an internationally-agreed implementation strategy for a surface pCO₂ network based on VOS, drifter and time series observations from the Surface Reference Mooring Network and other platforms together with associated products.

(Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523)

Additional Information:

• National Activities Summaries of Operational & Planned Observation Programs (Moorings, ARGO, Sea Level, XCTD/XBT/TSG, TS Hydrography, VOS, Sea Ice, Satellites, Black Sea, BOOS, NEAR-GOOS, Bio/Chem, Carbon, Coastal)

References:

• Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523
• The Second Report on the Adequacy of the Global Observing Systems for Climate in Support of the UNFCCC - April 2003 (GCOS-82/WMO/TD Noc 1143)

Data, Product, Metadata and Information Access

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