What is Ocean Acidification?
Since the beginning of the Industrial Revolution, when humans began burning coal in large quantities, the world’s ocean water has gradually become more acidic. Like global warming, this phenomenon, which is known as ocean acidification, is a direct consequence of increasing levels of carbon dioxide (CO2) in Earth’s atmosphere.
Prior to industrialization, the concentration of carbon dioxide in the atmosphere was 280 parts per million (ppm). With increased use of fossil fuels, that number is now approaching 400 ppm and the growth rate is accelerating. Scientists calculate that the ocean is currently absorbing about one quarter of the CO2 that humans are emitting. When CO2 combines with seawater, chemical reactions occur that reduce the seawater pH, hence the term ocean acidification.
Currently, about half of the anthropogenic (human-caused) CO2 in the ocean is found in the upper 400 meters (1,200 feet) of the water column, while the other half has penetrated into the lower thermocline and deep ocean. Density- and wind-driven circulation help mix the surface and deep waters in some high latitude and coastal regions, but for much of the open ocean, deep pH changes are expected to lag surface pH changes by a few centuries.
Ocean acidification and global warming are different problems, but are closely linked because they share the same root cause—human emissions of CO2. The atmospheric concentration of CO2 is now higher than it has been for the last 800,000 years and possibly higher than any time in the last 20 million years. Humans have thus far benefited from the ocean’s capacity to hold enormous amounts of carbon, including a large portion of this excess CO2. Had the ocean not absorbed such vast quantities of CO2, the atmospheric concentration would be even higher, and the environmental consequences of global warming (sea level rise, shifting weather patterns, more extreme weather events, etc.) and their associated socioeconomic impacts would likely be even more pronounced. However, the oceans cannot continue to absorb CO2 at the current rate without undergoing significant changes in chemistry, biology, and ecosystem structure.
What is Ocean Acidification?
Since the beginning of the Industrial Revolution, when humans began burning coal in large quantities, the world’s ocean water has gradually become more acidic. Like global warming, this phenomenon, which is known as ocean acidification, is a direct consequence of increasing levels of carbon dioxide (CO2) in Earth’s atmosphere.
Prior to industrialization, the concentration of carbon dioxide in the atmosphere was 280 parts per million (ppm). With increased use of fossil fuels, that number is now approaching 400 ppm and the growth rate is accelerating. Scientists calculate that the ocean is currently absorbing about one quarter of the CO2 that humans are emitting. When CO2 combines with seawater, chemical reactions occur that reduce the seawater pH, hence the term ocean acidification.
Currently, about half of the anthropogenic (human-caused) CO2 in the ocean is found in the upper 400 meters (1,200 feet) of the water column, while the other half has penetrated into the lower thermocline and deep ocean. Density- and wind-driven circulation help mix the surface and deep waters in some high latitude and coastal regions, but for much of the open ocean, deep pH changes are expected to lag surface pH changes by a few centuries.
Ocean acidification and global warming are different problems, but are closely linked because they share the same root cause—human emissions of CO2. The atmospheric concentration of CO2 is now higher than it has been for the last 800,000 years and possibly higher than any time in the last 20 million years. Humans have thus far benefited from the ocean’s capacity to hold enormous amounts of carbon, including a large portion of this excess CO2. Had the ocean not absorbed such vast quantities of CO2, the atmospheric concentration would be even higher, and the environmental consequences of global warming (sea level rise, shifting weather patterns, more extreme weather events, etc.) and their associated socioeconomic impacts would likely be even more pronounced. However, the oceans cannot continue to absorb CO2 at the current rate without undergoing significant changes in chemistry, biology, and ecosystem structure.
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