Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds

Abstract

Abstract. 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 ( arag ) climatologies for 12 open ocean, coastal, and coral reef locations using 3-hourly moored observations of surface seawater partial pressure of CO 2 and pH collected together since as early as 2010. Mooring observations suggest open ocean subtropical and subarctic sites experience present-day surface pH and 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 arag conditions surpass biologically relevant thresholds associated with ocean acidification impacts on Mytilus californianus ( arag < 1.8) and Crassostrea gigas ( arag < 2.0) larvae in the California Current Ecosystem (CCE) and Mya arenaria larvae in the Gulf of Maine ( arag < 1.6). At the most variable mooring locations in coastal systems of the CCE, subseasonal conditions approached 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 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.

Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean

“…The seasonal range of surface seawater p CO 2 at mean SST and DIC are higher at KEO and Papa compared to WHOTS and Stratus (Figure a). Similar patterns between sites were found in observations of sea surface pH and aragonite saturation state [ Sutton et al , ]. This difference is attributed to larger seasonality of SST and productivity compared to the oligotrophic subtropical waters where WHOTS and Stratus reside.…”

Examining the Impact of Tropical Cyclones on Air‐Sea CO2 Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

“…The x CO 2 measurement was made by a LI‐820, LI‐COR gas analyzer calibrated with reference gases traceable to World Meteorological Organization standards. A Sea‐Bird Electronics 16 plus V2 SeaCAT was also deployed and integrated with the MAPCO 2 system to make SST and SSS measurements used to calculate pCO 2 (Dickson et al, ; Sutton et al, ; Weiss, ). The accuracy of measuring the SST and SSS was about ±0.02 °C and ±0.02 psu, respectively (McPhaden et al, ).…”

Hawaii Coastal Seawater CO2 Network: A Statistical Evaluation of a Decade of Observations on Tropical Coral Reefs

“…To help resolve this problem, high-resolution monitoring of seawater partial pressure of CO 2 (pCO 2 sw) on surface buoys in coastal regions began late in 2005 (see Massaro et al, 2012). Ocean carbonate chemistry research conducted in various coastal settings (Drupp et al, 2011(Drupp et al, , 2013Yan et al, 2011Yan et al, , 2016Massaro et al, 2012;Bates et al, 2014;Sutton et al, 2014aSutton et al, , 2016 has shown that, in order to understand the drivers of natural variability and identify longterm trends, it is necessary to gain better insight into the processes that control marine CO 2 concentrations, including the direction and magnitude of the air-sea CO 2 flux.…”