This «acidification» of global oceans is observed as lower pH levels. (wxshift.com)
The immediate cause is clear: the ongoing rise in global ocean temperatures that comes from climate change. (350.org)
Change in global ocean heat content between the surface and 2000 meters of depth from 1958 to 2017 (top) and distribution of ocean heat content anomalies in 2017 (bottom). (carbonbrief.org)