Abstract.In an intensifying effort to track ocean change and distinguish between natural and anthropogenic drivers, sustained ocean time series measurements are becoming increasingly important. Advancements in the ocean carbon observation network over the last decade, such as the development and deployment of Moored Autonomous pCO 2 (MAPCO 2 ) systems, have dramatically improved our ability to characterize ocean climate, sea-air gas exchange, and biogeochemical processes. The MAPCO 2 system provides high-resolution data that can measure interannual, seasonal, and sub-seasonal dynamics and constrain the impact of shortterm biogeochemical variability on carbon dioxide (CO 2 ) flux. Overall uncertainty of the MAPCO 2 using in situ calibrations with certified gas standards and post-deployment standard operating procedures is < 2 µatm for seawater partial pressure of CO 2 (pCO 2 ) and < 1 µatm for air pCO 2 . The MAPCO 2 maintains this level of uncertainty for over 400 days of autonomous operation. MAPCO 2 measurements are consistent with shipboard seawater pCO 2 measurements and GLOBALVIEW-CO2 boundary layer atmospheric values. Here we provide an open-ocean MAPCO 2 data set including over 100 000 individual atmospheric and seawater pCO 2 measurements on 14 surface buoys from 2004 through 2011 and a description of the methods and data quality control involved. The climate-quality data provided by the MAPCO 2 have allowed for the establishment of open-ocean observatories to track surface ocean pCO 2 changes around the globe. Data are available at doi:10.3334/CDIAC/OTG.TSM_NDP092 and http://cdiac.ornl.gov/oceans/Moorings/ndp092.

Abstract. Ship-based time series, some now approaching over 3 decades long, are critical climate records that have dramatically improved our ability to characterize natural and anthropogenic drivers of ocean carbon dioxide (CO2) uptake and biogeochemical processes. Advancements in autonomous marine carbon sensors and technologies over the last 2 decades have led to the expansion of observations at fixed time series sites, thereby improving the capability of characterizing sub-seasonal variability in the ocean. Here, we present a data product of 40 individual autonomous moored surface ocean pCO2 (partial pressure of CO2) time series established between 2004 and 2013, 17 also include autonomous pH measurements. These time series characterize a wide range of surface ocean carbonate conditions in different oceanic (17 sites), coastal (13 sites), and coral reef (10 sites) regimes. A time of trend emergence (ToE) methodology applied to the time series that exhibit well-constrained daily to interannual variability and an estimate of decadal variability indicates that the length of sustained observations necessary to detect statistically significant anthropogenic trends varies by marine environment. The ToE estimates for seawater pCO2 and pH range from 8 to 15 years at the open ocean sites, 16 to 41 years at the coastal sites, and 9 to 22 years at the coral reef sites. Only two open ocean pCO2 time series, Woods Hole Oceanographic Institution Hawaii Ocean Time-series Station (WHOTS) in the subtropical North Pacific and Stratus in the South Pacific gyre, have been deployed longer than the estimated trend detection time and, for these, deseasoned monthly means show estimated anthropogenic trends of 1.9±0.3 and 1.6±0.3 µatm yr−1, respectively. In the future, it is possible that updates to this product will allow for the estimation of anthropogenic trends at more sites; however, the product currently provides a valuable tool in an accessible format for evaluating climatology and natural variability of surface ocean carbonate chemistry in a variety of regions. Data are available at https://doi.org/10.7289/V5DB8043 and https://www.nodc.noaa.gov/ocads/oceans/Moorings/ndp097.html (Sutton et al., 2018).

In an intensifying effort to track ocean change and distinguish between natural and anthropogenic drivers, sustained ocean time series measurements are becoming increasingly important. Advancements in the ocean carbon observation network over the last decade, such as the development and deployment of Moored Autonomous pCO 2 (MAPCO 2) systems, have dramatically improved our ability to characterize ocean climate , sea-air gas exchange, and biogeochemical processes. The MAPCO 2 system provides high-resolution data that can measure interannual, seasonal, and sub-seasonal dynamics and constrain the impact of short-term biogeochemical variability on carbon dioxide (CO 2) flux. Overall uncertainty of the MAPCO 2 using in situ calibrations with certified gas standards and post-deployment standard operating procedures is < 2 µatm for seawater partial pressure of CO 2 (pCO 2) and < 1 µatm for air pCO 2. The MAPCO 2 maintains this level of uncertainty for over 400 days of autonomous operation. MAPCO 2 measurements are consistent with ship-board seawater pCO 2 measurements and GLOBALVIEW-CO2 boundary layer atmospheric values. Here we provide an open-ocean MAPCO 2 data set including over 100 000 individual atmospheric and seawater pCO 2 measurements on 14 surface buoys from 2004 through 2011 and a description of the methods and data quality control involved. The climate-quality data provided by the MAPCO 2 have allowed for the establishment of open-ocean observatories to track surface ocean pCO 2 changes around the globe. Data are available at doi:10.3334/CDIAC/OTG.TSM_NDP092 and http://cdiac.ornl.gov/oceans/Moorings/ndp092.