Future declines in subsurface pH  will be modulated by changes in ocean overturning and water-mass subduction , and in organic matter remineralisation . In particular, decreases in pH will be less consistent at the seafloor than at the surface and will be linked to the transport of surface anomalies to depth. For example, >20% of the North Atlantic seafloor deeper than 500 m, including canyons and seamounts designated as marine protected areas , will experience pH reductions >0.2 by 2100 under RCP8.5 . Changes in pH in the abyssal ocean  are greatest in the Atlantic and Arctic Oceans, with lesser impacts in the Southern and Pacific Oceans by 2100, mainly due to ventilation time scales .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report