Ocean acidification: Why, How and So What?
Andreas J. Andersson, Scripps Institution of Oceanography
As a result of human activities including burning of fossil fuels, cement production, land use changes and deforestation, atmospheric CO2 concentration has increased from approximately 280 ppm to 400 ppm since the preindustrial revolution. However, only about half of the CO2 released to the atmosphere has accumulated there. The other half has been partitioned between uptake by the oceans and the terrestrial biosphere. As a result, the surface ocean pH has on average decreased by 0.1 units and is expected to decrease by an additional 0.3 to 0.4 units by the end of this century if CO2 emissions continue to increase at the current rate. Unequivocal evidence of the ongoing ocean acidification exists from multiple time-series locations around the world. In addition, based on basic chemical principles, we can fairly accurately predict future open ocean surface seawater pH for any given CO2 emission scenario. However, many questions still remain on how these changes in seawater chemistry will affect individual organisms, communities, ecosystems, food webs and biogeochemical cycles. Scientists from many different disciplines use a range of approaches to address these questions including experimental manipulations, field observations, numerical modeling as well as the geological record for potential analogues.