Recent studies (Katavouta et al., 2018; Jiang et al., 2019; Arora et al., 2020; Rodgers et al., 2020) suggest with medium confidence that the decrease in the ocean CO 2 uptake ratio to anthropogenic CO 2 emissions, under low to no mitigation scenarios over the 21st century, is predominantly attributable to the ocean carbon- concentration feedback through the reduction of the seawater CO 2 buffering capacity, but with contributions from physical drivers such as warming and wind stress (medium confidence) and biological drivers