Ocean acidification is a result of the ocean absorbing anthropogenic CO₂, leading to significant changes in seawater chemistry. This process lowers pH, reduces carbonate ion concentrations, and decreases the saturation states of calcium carbonate minerals like calcite and aragonite. By the end of this century, under high CO₂ emission scenarios, surface ocean pH is projected to drop from 8.2 to 7.8, a 150% increase in ocean acidity. Aragonite undersaturation is expected to begin in the Arctic Ocean by 2020 and the Southern Ocean by 2050, with all of the Arctic becoming undersaturated by 2050 and parts of the North Pacific by 2095. For calcite, undersaturation will occur by 2095 in most of the Arctic and parts of the Bering and Chukchi Seas. These changes will impact calcifying organisms such as planktonic coccolithophores, pteropods, mollusks, and corals, which rely on carbonate ions to form their shells and skeletons. The ocean's ability to absorb CO₂ is also influenced by marine carbonate interactions, with the dissolution reaction playing a key role. The saturation states of carbonate minerals decrease with depth due to biological respiration and cold temperatures in deep seawater. The locations of the saturation horizon, where seawater becomes undersaturated with respect to calcium carbonate, will shift as ocean acidification progresses. The projected changes in saturation states will have significant implications for marine ecosystems, particularly for high-latitude calcifying organisms. The study highlights the urgent need to address anthropogenic CO₂ emissions to mitigate the impacts of ocean acidification on marine life and ecosystems.Ocean acidification is a result of the ocean absorbing anthropogenic CO₂, leading to significant changes in seawater chemistry. This process lowers pH, reduces carbonate ion concentrations, and decreases the saturation states of calcium carbonate minerals like calcite and aragonite. By the end of this century, under high CO₂ emission scenarios, surface ocean pH is projected to drop from 8.2 to 7.8, a 150% increase in ocean acidity. Aragonite undersaturation is expected to begin in the Arctic Ocean by 2020 and the Southern Ocean by 2050, with all of the Arctic becoming undersaturated by 2050 and parts of the North Pacific by 2095. For calcite, undersaturation will occur by 2095 in most of the Arctic and parts of the Bering and Chukchi Seas. These changes will impact calcifying organisms such as planktonic coccolithophores, pteropods, mollusks, and corals, which rely on carbonate ions to form their shells and skeletons. The ocean's ability to absorb CO₂ is also influenced by marine carbonate interactions, with the dissolution reaction playing a key role. The saturation states of carbonate minerals decrease with depth due to biological respiration and cold temperatures in deep seawater. The locations of the saturation horizon, where seawater becomes undersaturated with respect to calcium carbonate, will shift as ocean acidification progresses. The projected changes in saturation states will have significant implications for marine ecosystems, particularly for high-latitude calcifying organisms. The study highlights the urgent need to address anthropogenic CO₂ emissions to mitigate the impacts of ocean acidification on marine life and ecosystems.