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Information about Ocean Acidification

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Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s


Ocean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104 (a change of -0.075)[1][2].

Carbon cycle

Pollution
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Air pollution
Acid rain • Air Quality Index • Atmospheric dispersion modeling • Chlorofluorocarbon • Global dimming • Global warming • Haze • Indoor air quality • Ozone depletion • Particulate • Smog
Water pollution
Eutrophication • Hypoxia • Marine pollution • Ocean acidification • Oil spill • Ship pollution • Surface runoff • Thermal pollution • Wastewater • Waterborne diseases • Water quality • Water stagnation
Soil contamination
Bioremediation • Herbicide • Pesticide •Soil Guideline Values (SGVs)
Radioactive contamination
Actinides in the environment • Environmental radioactivity • Fission product • Nuclear fallout • Plutonium in the environment • Radiation poisoning • radium in the environment • Uranium in the environment
Other types of pollution
Invasive species • Light pollution • Noise pollution • Radio spectrum pollution • Visual pollution
Inter-government treaties
Montreal Protocol • Nitrogen Oxide Protocol • Kyoto Protocol • CLRTAP
Major organizations
DEFRA • EPA • Global Atmosphere Watch • Greenpeace • National Ambient Air Quality Standards
Related topics
Natural environment
In the natural carbon cycle, the atmospheric concentration of carbon dioxide (CO2) represents a balance of fluxes between the oceans, terrestrial biosphere and the atmosphere. Human activities such as land-use changes, the combustion of fossil fuels, and the production of cement have led to a new flux of CO2 into the atmosphere. Some of this has remained in the atmosphere (where it is responsible for the rise in atmospheric concentrations), some is believed to have been taken up by terrestrial plants, and some has been absorbed by the oceans.

When CO2 dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species : dissolved free carbon dioxide (CO2 (aq)), carbonic acid (H2CO3), bicarbonate (HCO3-) and carbonate (CO32-). The ratio of these species depends on factors such as seawater temperature and alkalinity (see the article on the ocean's solubility pump for more detail).

Acidification

Average surface ocean pH[1]
Time pH pH change Source
Pre-industrial (1700s)8.1790.000analysed field[2]
Present-day (1994)8.104-0.075field[2]
2050 (2×CO2 = 560 ppm)7.949-0.230model[1]
2100 (IS92a)[3]7.824-0.355model[1]


Dissolving CO2 in seawater also increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH. The use of the term "ocean acidification" to describe this process was introduced in Caldeira and Wickett (2003)[4]. Since the industrial revolution began, ocean pH has dropped by approximately 0.1 units (on the logarithmic scale of pH), and it is estimated that it will drop by a further 0.3 - 0.5 units by 2100 as the ocean absorbs more anthropogenic CO2[4][1][5]. Note that, although the ocean is acidifying, its pH is still greater than 7 (that of neutral water), so the ocean could also be described as becoming less alkaline.

Possible Impacts

Although the natural absorption of CO2 by the world's oceans helps mitigate the climatic effects of anthropogenic emissions of CO2, it is believed that the resulting decrease in pH will have negative consequences, primarily for oceanic calcifying organisms. These use the calcite or aragonite polymorphs of calcium carbonate to construct cell coverings or skeletons. Calcifiers span the food chain from autotrophs to heterotrophs and include organisms such as coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs.

Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion, and when carbonate becomes under-saturated, structures made of calcium carbonate are vulnerable to dissolution. Research has already found that corals[6], coccolithophore algae[7], foraminifera[8], shellfish[9] and pteropods[1] experience reduced calcification or enhanced dissolution when exposed to elevated CO2. The Royal Society of London published a comprehensive overview of ocean acidification, and its potential consequences, in June 2005[5].

While the full ecological consequences of these changes in calcification are still uncertain, it appears likely that calcifying species will be adversely affected. There is also some evidence that the effect of acidification on coccolithophores (among the most abundant phytoplankton in the ocean) in particular may eventually exacerbate climate change, by decreasing the earth's albedo via their effects on oceanic cloud cover[10].

Aside from calcification (and specifically calcifiers), organisms may suffer other adverse effects, either directly as reproductive or physiological effects (e.g. CO2-induced acidification of body fluids, known as hypercapnia), or indirectly through negative impacts on food resources. However, as with calcification, as yet there is not a full understanding of these processes in marine organisms or ecosystems.

Gallery

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Sea surface "present day" (1990s) anthropogenic CO2
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Vertical inventory of "present day" (1990s) anthropogenic CO2
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Change in surface CO32- ion from the 1700s to the 1990s

See also

References

1. ^ Orr, James C.; Fabry, Victoria J.; Aumont, Olivier; Bopp, Laurent; Doney, Scott C.; Feely, Richard A. et al. (2005). "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms". Nature 437 (7059): 681-686. DOI:10.1038/nature04095. ISSN 0028-0836. 
2. ^ Key, R.M.; Kozyr, A.; Sabine, C.L.; Lee, K.; Wanninkhof, R.; Bullister, J.; Feely, R.A.; Millero, F.; Mordy, C. and Peng, T.-H. (2004). "A global ocean carbon climatology: Results from GLODAP". Global Biogeochemical Cycles 18: GB4031. DOI:10.1029/2004GB002247. ISSN 0886-6236. 
3. ^ Review of Past IPCC Emissions Scenarios, IPCC Special Report on Emissions Scenarios (ISBN 0521804930).
4. ^ Caldeira, K.; Wickett, M.E. (2003). "Anthropogenic carbon and ocean pH". Nature 425 (6956): 365-365. DOI:10.1038/425365a. ISSN 0028-0836. 
5. ^ Raven, J. A. et al. (2005). Ocean acidification due to increasing atmospheric carbon dioxide. Royal Society, London, UK.
6. ^ Gattuso, J.-P.; Frankignoulle, M.; Bourge, I.; Romaine, S. and Buddemeier, R. W. (1998). "Effect of calcium carbonate saturation of seawater on coral calcification". Global and Planetary Change 18 (1-2): 37-46. DOI:10.1016/S0921-8181(98)00035-6. ISSN 0921-8181. 
7. ^ Riebesell, Ulf; Zondervan, Ingrid; Rost, Björn; Tortell, Philippe D.; Zeebe, Richard E. and François M. M. Morel (2000). "Reduced calcification of marine plankton in response to increased atmospheric CO2". Nature 407 (6802): 364-367. DOI:10.1038/35030078. ISSN 0028-0836.  (Subscription required)
8. ^ Phillips, Graham, Chris Branagan. "Ocean Acidification – The BIG global warming story", ABC TV Science: Catalyst, Australian Broadcasting Corporation, 2007-09-13. Retrieved on 2007-09-18. 
9. ^ Gazeau, F.; Quiblier, C.; Jansen, J. M.; Gattuso, J.-P.; Middelburg, J. J. and Heip, C. H. R. (2007). "Impact of elevated CO2 on shellfish calcification". Geophysical Research Letters 34: L07603. DOI:10.1029/2006GL028554. ISSN 0094-8276. 
10. ^ Ruttiman, J. (2006). "Sick Seas". Nature 442 (7106): 978-980. DOI:10.1038/442978a. ISSN 0028-0836.  (Subscription required)

Further reading

External links

Carbonate system calculators

The following packages calculate the state of the carbonate system in seawater (including pH):
 •  • [ e]
Global warming and Climate change
TemperaturesInstrumental record Satellite record Past 1000 years Since 1880 Geologic record
CausesScientific opinion on climate change
Anthropogenic: Carbon dioxide Climate sensitivity Deforestation Global dimming Global warming potential Greenhouse effect Greenhouse gases Keeling Curve Urban heat island
Natural: Cloud forcing Glaciation Global cooling Ocean variability Orbital variations Plate tectonics Radiative forcing Solar variation Volcanism
ModelsGlobal climate model
IssuesOzone depletion Ocean acidification
PoliticsGlobal warming controversy Intergovernmental Panel on Climate Change Scientists opposing the mainstream assessment
EffectsSea level rise Glacier retreat Climate change and agriculture National Assessment on Climate Change Economics of global warming Shutdown of thermohaline circulation
MitigationIndividual and political action on climate change
Kyoto Protocol: Clean Development Mechanism
Schemes: Emissions trading Personal carbon trading Carbon tax Carbon offsets Carbon dioxide sink (Carbon sequestration)
Energy conservation: Efficient energy use Renewable energy Renewable energy commercializationRenewable energy development Soft energy path
AdaptationUnited Kingdom Climate Change Programme European Climate Change Programme
    pH is a measure of the acidity or alkalinity of a solution. Aqueous solutions at 25 ℃ with a pH less than seven are considered acidic, while those with a pH greater than seven are considered basic (alkaline). The pH of 7.
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    Anthropogenic effects, processes, objects, or materials are those that are derived from human activities, as opposed to those occurring in natural environments without human influences.
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    Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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    Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.
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    Pollution is the introduction of pollutants (whether chemical substances, or energy such as noise, heat, or light) into the environment to such a point that its effects become harmful to human health, other living organisms, or the environment.
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    The term "acid rain" is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. The more accurate term is "acid precipitation." Distilled water, which contains no carbon dioxide, has a neutral pH of 7.
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    Air Quality Index (AQI) is a standardized indicator of the air quality in a given location. It measures mainly ground-level ozone and particulates (except the pollen count), but may also include sulphur dioxide, and nitrogen dioxide.
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    Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that solve the mathematical equations and algorithms which simulate the pollutant dispersion.
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    Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in 1950s.
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    Global warming refers to the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.

    The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.
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    HaZe is a X window manager extensively based on the Takashi Hasegawa creation known as MLVWM, the Apple Macintosh interface-mimicking window manager.

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    Indoor Air Quality (IAQ) deals with the content of interior air that could affect health and comfort of building occupants. The IAQ may be compromised by microbial contaminants (mold, bacteria), chemicals (such as carbon monoxide, radon), allergens, or any mass or energy stressor
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    Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions
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    Although natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and
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    Eutrophication, strictly speaking, means an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. It may occur on land or in water.
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