UNDER REVIEW AT NATURE-- DO NOT QUOTE OR CITE FOR COLLEAGUES AT AGCI MEETING ONLY--NOT FOR GENERAL DISTRIBUTION Anthropogenic carbon and ocean pH

• Main Authors: K. Caldeira, Michael E. Wickett
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Methane hydrate
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.319.9812; http://www.agci.org/dB/PDFs/03S2_KCaldeira_OceanPh.pdf

Most fossil-fuel CO2 released to the atmosphere will eventually be absorbed by the ocean 1 with potentially adverse consequences for marine biota 2–4. We quantify pH changes that may result from continued release of fossil-fuel CO2 to the atmosphere, and compare these with pH changes inferred from geological and historical records. We conclude that releasing fossil-fuel CO2 to the atmosphere over several centuries may result in ocean pH changes greater than any inferred from the geologic record of the past 300 million years, with the possible exception of rare extreme events such as bolide impacts or catastrophic methane hydrate degassing. When carbon dioxide dissolves in the ocean it increases the hydrogen-ion concentration, lowering ocean pH (i.e., negative common log of the hydrogen ion activity). Due to a paucity of relevant observations, we have a limited understanding of the effects of pH reductions on marine biota. Coral reefs 2, calcareous plankton 3, and other organisms with calcium carbonate skeletal material or shells may be particularly impacted by decreased ocean pH. Most biota resides primarily near the surface where greatest pH change can be expected to occur, but deep ocean biota may be more sensitive to pH changes 4.