Ocean acidification is a sustained decrease in seawater pH, commonly caused by absorption of atmospheric carbon dioxide. Dissolved carbon dioxide shifts chemical equilibrium toward bicarbonate and hydrogen ions. Reactions involving carbonate buffer part of the perturbation while reducing carbonate availability.
The change can affect the conditions for forming or dissolving calcium carbonate, even while the water remains alkaline with a pH above seven. Characterizing the carbonate system requires measurements such as pH, dissolved inorganic carbon, carbon-dioxide partial pressure or alkalinity, together with temperature and salinity. Two suitable independent carbonate-system measurements constrain the others through an equilibrium model.[ref]
What is Ocean Acidification by NOAA Ocean Acidification Program. Seawater chemistry, buffering and monitoring the four carbonate-system parameters
Ocean acidification refers to the process by which the pH level of Earth's oceans decreases due to the absorption of excess atmospheric carbon dioxide (CO2). As CO2 is emitted into the atmosphere from human activities, such as burning fossil fuels and deforestation, a significant portion of it is absorbed by the oceans. When CO2 dissolves in seawater, it reacts with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions.
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