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).

The accuracies of the meteorological sensors (air temperature, relative humidity, barometric pressure, near-surface temperature, longwave and shortwave radiation, and wind speed and direction) that compose the Improved Meteorological (IMET) system used on buoys at long-term ocean time series sites known as ocean reference stations (ORS) are analyzed to determine their absolute error characteristics. The predicted errors are compared to in situ measurement discrepancies and other observations (direct flux shipboard sensors) to confirm the predictions. The meteorological errors are then propagated through bulk flux formulas and the Coupled Ocean–Atmosphere Response Experiment (COARE) algorithm to give predicted errors for the heat flux components, the freshwater flux, and the momentum flux. Absolute errors are presented for three frequency bands [instantaneous (1-min sampling), diurnal, and annual]. The absolute uncertainty in the annually averaged net heat flux is found to be 8 W m−2 for conditions similar to the current ORS deployments in the subtropics.

Variability and change in the ocean sink of anthropogenic carbon dioxide (CO₂) have implications for future climate and ocean acidification. Measurements of surface seawater CO₂ partial pressure (pCO₂) and wind speed from moored platforms are used to calculate high‐resolution CO₂ flux time series. Here we use the moored CO₂ fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO₂, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO₂ uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO₂ values driven by warm anomalies cause this region to be a net annual CO₂ source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO₂ sink to source.

One of the major challenges to assessing the impact of ocean acidification on marine life is detecting and interpreting long-term change in the context of natural variability. This study addresses this need through a global synthesis of monthly pH and aragonite saturation state (Ω_arag) climatologies for 12 open ocean, coastal, and coral reef locations using 3-hourly moored observations of surface seawater partial pressure of CO₂ and pH collected together since as early as 2010. Mooring observations suggest open ocean subtropical and subarctic sites experience present-day surface pH and Ω_arag conditions outside the bounds of preindustrial variability throughout most, if not all, of the year. In general, coastal mooring sites experience more natural variability and thus, more overlap with preindustrial conditions; however, present-day Ω_arag conditions surpass biologically relevant thresholds associated with ocean acidification impacts on Mytilus californianus (Ω_arag < 1.8) and Crassostrea gigas (Ω_arag < 2.0) larvae in the California Current Ecosystem (CCE) and Mya arenaria larvae in the Gulf of Maine (Ω_arag < 1.6). At the most variable mooring locations in coastal systems of the CCE, subseasonal conditions approached Ω_arag = 1. Global and regional models and data syntheses of ship-based observations tended to underestimate seasonal variability compared to mooring observations. Efforts such as this to characterize all patterns of pH and Ω_arag variability and change at key locations are fundamental to assessing present-day biological impacts of ocean acidification, further improving experimental design to interrogate organism response under real-world conditions, and improving predictive models and vulnerability assessments seeking to quantify the broader impacts of ocean acidification.

Recent observations of surface meteorology and exchanges of heat, freshwater, and momentum between the ocean and the atmosphere in the Bay of Bengal are presented. These observations characterize air-sea interaction at 18 degrees N, 89.5 degrees E from December 2014 to January 2016 and also at other locations in the northern Bay of Bengal. Monsoonal variability dominated the records, with winds to the northeast in summer and to the southwest in winter. This variability included a strong annual cycle in the atmospheric forcing of the ocean in the Bay of Bengal, with the winter monsoon marked by sustained ocean heat loss resulting in ocean cooling, and the summer monsoon marked by strong storm events with dark skies and rain that also resulted in ocean cooling. The spring intermonsoon was a period of clear skies and low winds, when strong solar heating and weak wind-driven mixing led to ocean warming. The fall intermonsoon was a transitional period, with some storm events but also with enough clear skies and sunlight that ocean surface temperature rose again. Mooring and shipboard observations are used to examine the ability of model-based surface fluxes to represent air-sea interaction in the Bay of Bengal; the model-based fluxes have significant errors. The surface forcing observed at 18 degrees N is also used together with a one-dimensional ocean model to illustrate the potential for local air-sea interaction to drive upper-ocean variability in the Bay of Bengal

Sustained ocean observations benefit many users and societal goals but could benefit many more. Such information is critical for using ocean resources responsibly and sustainably as the ocean becomes increasingly important to society. The contributions of many nations cooperating to develop the Global Ocean Observing System has resulted in a strong base of global and regional ocean observing networks. However, enhancement of the existing observation system has been constrained by flat funding and limited cooperation among present and potential users. At the same time, a variety of actors are seeking new deployments in remote and newly ice-free regions and new observing capabilities, including biological and biogeochemical sensors. Can these new needs be met? In this paper, a vision for how to sustain ocean observing in the future is presented. A key evolution will be to grow the pool of users, engaging end users across society. Users with shared values need to be brought together with commitment to sustainable use of the ocean in the broadest sense. Present planning for sustained observations builds on the development of the Global Ocean Observing System which has primarily targeted increased scientific understanding of ocean processes and of the ocean's role in climate. We must build on that foundation to develop an Ocean Partnership for Sustained Observing that will incorporate the growing needs of a broad constituency of users beyond climate and make the case for new resources. To be most effective this new Partnership should incorporate the principles of a collective impact organization, enabling closer engagement with the private sector, philanthropies, governments, NGOs, and other groups. Steps toward achieving this new Partnership are outlined in this paper, with the intent of establishing it early in the UN Decade of Ocean Science.