[Ocean] Acidification

The uptake of anthropogenic change within part of the climate system that can be attributed to human action, rather than natural causes. carbon since 1750 has led to the oceans becoming more acidic with an average decrease in pH of 0.1 units. Surface ocean and UK coastal water pH will continue to rapidly decline in the future as they take up more atmospheric CO2.

Although the effects of the current reduction in pH on the marine biosphere are as yet undocumented this is due, in part, to lack of research in this area. However, unless we substantially and urgently reduce CO2 emissions, experiments, observations and modelling indicate that future reductions in ocean acidity will have major negative impacts on aragonitic and calcitic (shell/skeleton) forming organisms this century and their dependent species. There is growing evidence that the physiology (e.g. growth and reproduction) of adults, larvae and juveniles of some species are sensitive to acidification. Impacts of decreasing pH on key biogeochemical processes other than calcification is theoretically possible and serious (e.g. impact on nutrient speciation, primary production and nutrient, carbon and sulphur cycling,) but there has been little research on this. The knock-on effects of ocean acidification on marine ecosystems, biogeochemical cycles, food webs and biodiversity could be considerable but difficult to quantify. Reducing CO2 emissions is the only way of reducing ocean acidification.

Nearly half of the CO2 derived from burning fossil fuel has already been absorbed by the surfaces of our seas and oceans and more will be absorbed in the future as we continue to increase our CO2 emissions to the atmosphere. The ocean uptake of CO2 is effectively buffering even more serious climate change than that predicted by clear evidence-based scientific consensus. Continued acidification will reduce the ability of the ocean to take up CO2 from the atmosphere, which will have feedbacks to future climate change, further accelerating the accumulation of CO2 in the atmosphere.

Marine Climate Change Impacts Partnership, Carol Turley, 11 January 2008. Web site.

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