Air–sea CO2 exchange and ocean acidification in UK seas and adjacent waters

• Main Authors: Humphreys, MP, Artioli, Y, Bakker, DCE, Hartman, SE, León, P, Wakelin, S, Walsham, P, Williamson, P
• Format: Report
• Language: English
• Published: MCCIP Science Review 2020 2020
• Subjects: Williamson; North Atlantic; Ocean acidification
• Online Access: https://plymsea.ac.uk/id/eprint/8882/; https://plymsea.ac.uk/id/eprint/8882/1/03_ocean_acidification_2020.pdf; https://ueaeprints.uea.ac.uk/id/eprint/73767; https://doi.org/10.14465/2020.arc03.oac

Ongoing anthropogenic emissions of carbon dioxide (CO2) into the atmosphere are driving a net flux of CO2 into the ocean globally, resulting in a decline in pH called ‘ocean acidification’. Here, we discuss the consequences of this for the seas surrounding the UK from a chemical perspective, focussing on studies published since the previous MCCIP review of ocean acidification research (Williamson et al., 2017). In this reporting cycle, the biological, ecological, and socio-economic impacts of ocean acidification are considered in more detail in separate accompanying MCCIP reviews. The atmospheric CO2 concentration continues to increase due to human activities (Le Quéré et al., 2018), increasing the net flux of CO2 into the global ocean, including the North Atlantic and UK continental shelf seas. Such CO2 uptake has the desirable effect of reducing the rate of climate change, but the undesirable result of ocean acidification. Our understanding of the factors that drive high spatial and temporal variability in air-sea CO2 fluxes and seawater pH in UK waters has continued to improve, thanks to observational campaigns both across the entire North-West European continental shelf sea and at specific time–series sites. Key challenges for the future include sustaining time–series observations of near-surface marine carbonate system variables, and of the auxiliary parameters required for their interpretation (e.g. temperature, salinity, and nutrients); developing and deploying new sensor technology for full water-column profiles and pore waters in seafloorsediments; and increasing the spatial and temporal resolution of models sufficiently to capture the complex processes that dominate the marine carbonate system in coastal and shelf sea environments, along with improving how those processes are themselves simulated.