HR: 17:15h
AN: B54B-06    [Abstracts]
TI: Ocean Acidification Consequences of Stabilization of Atmospheric Carbon Dioxide
AU: * Cao, L
EM: longcao@stanford.edu
AF: Department of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AU: Caldeira, K
EM: kcaldeira@stanford.edu
AF: Department of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AB: We investigate ocean chemistry changes that would result from the stabilization of atmospheric carbon dioxide concentrations at different levels. To determine the fate of ocean chemistry after atmospheric carbon dioxide is stabilized, we perform a suite of simulations using the UVic Earth system model in which atmospheric CO2 is stabilized at levels ranging from 280 ppm to 5000 ppm. Atmospheric carbon dioxide is absorbed by the ocean, and makes the ocean more acidic (lowers ocean pH), decreasing carbonate-ion concentrations. These changes in ocean chemistry have the potential to significantly affect marine organisms. For example, a decrease in the saturation state of calcium carbonate minerals (aragonite and calcite) associated with the decrease in carbonate ion concentration will pose a great threat to the growth of calcifying organisms such as reef-building corals and pteropods. Before the industrial revolution, over 99 per cent of warm water coral reefs were bathed with open ocean waters with aragonite saturation greater than 3.25. If atmospheric carbon dioxide concentrations stabilize at 550 ppm, only 2 per cent of existing coral reefs will be in such environments. Even with atmospheric CO2 stabilization at 450 ppm, parts of the Southern Ocean will become undersaturated with respect to aragonite, causing the shells of pteropods to dissolve. At 450 ppm, about 10 per cent of the global ocean will have experienced a pH reduction greater than 0.2 units, violating US EPA water quality criteria for pH changes in open ocean waters. These changes in ocean chemistry are largely independent of the amount of climate change. Thus, consideration of biological consequences of ocean chemistry changes may favor lower atmospheric CO2 stabilization targets than might be selected based on consideration of climate change consequences alone.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0460 Marine systems (4800)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4220 Coral reef systems (4916)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting