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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L05607, doi:10.1029/2006GL028605, 2007

Effects of carbon dioxide and climate change on ocean acidification and carbonate mineral saturation

Long Cao

Department of Atmospheric Sciences, University of Illinois, Urbana, Illinois, USA


Ken Caldeira

Department of Global Ecology, Carnegie Institution, Stanford, California, USA


Atul K. Jain

Department of Atmospheric Sciences, University of Illinois, Urbana, Illinois, USA


Abstract

We use an earth system model of intermediate complexity to show how consideration of climate change affects predicted changes in ocean pH and calcium carbonate saturation state. Our results indicate that consideration of climate change produces second-order modifications to ocean chemistry predictions made with constant climate; these modifications occur primarily as a result of changes in sea surface temperature, and climate-induced changes in dissolved inorganic carbon concentrations. Under a CO2 emission scenario derived from the WRE1000 CO2 stabilization concentration pathway and a constant climate, we predict a 0.47 unit reduction in surface ocean pH relative to a pre-industrial value of 8.17, and a reduction in the degree of saturation with respect to aragonite from a pre-industrial value of 3.34 to 1.39 by year 2500. With the same CO2 emissions but the consideration of climate change under a climate sensitivity of 2.5°C the reduction in projected global mean surface pH is about 0.48 and the saturation state of aragonite decreases to 1.50. With a climate sensitivity of 4.5°C, these values are 0.51 and 1.62, respectively. Our study therefore suggests that future changes in ocean acidification caused by emissions of CO2 to the atmosphere are largely independent of the amounts of climate change.

Received 27 October 2006; accepted 31 January 2007; published 9 March 2007.

Keywords: carbon dioxide; climate change; ocean acidification.

Index Terms: 0460 Biogeosciences: Marine systems (4800); 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4504); 4806 Oceanography: Biological and Chemical: Carbon cycling (0428).

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Citation: Cao, L., K. Caldeira, and A. K. Jain (2007), Effects of carbon dioxide and climate change on ocean acidification and carbonate mineral saturation, Geophys. Res. Lett., 34, L05607, doi:10.1029/2006GL028605.