About Ocean Acidification
The ocean absorbs up to 30% of the annual emissions of anthropogenic CO2 to the atmosphere, helping to alleviate the impacts of climate change on the planet. However, this comes at a steep ecological cost, as the absorbed CO2 reacts in seawater and results in changing acidity levels in the ocean. The changing acidity is described by a decrease in seawater pH and closely linked shifts in the carbonate chemistry of the waters including the aragonite saturation state, which is the main form of calcium carbonate used by key species to form shells and skeletal material (e.g. reef building corals and shelled mollusks). Since the industrial revolution mean surface ocean pH has dropped by 0.1 units, corresponding to an increase in acidity of 26%. If CO2 emissions continue at the present rate, mean surface pH is predicted to fall by another 0.3 to 0.4 units (equivalent to a 100-150% increase in acidity) by the end of this century.
Concerns about ocean acidification, first expressed in the early 1980s, have been confirmed. Ocean acidification impacts global marine chemistry, essential biological processes are also affected, sometimes in critical ways. Furthermore, dissolved CO2 levels may influence the physiology of marine organisms, which often depend on a narrow range of environmental parameters including dissolved CO2 and pH.
Observations of marine acidity at open ocean and coastal locations have revealed that present-day conditions are often outside preindustrial bounds. In some regions, the changes are amplified by natural processes like upwelling (cold often, CO2 and nutrient rich water from the deep rises toward the sea surface), resulting in conditions outside biologically relevant thresholds.
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