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Journal of Geophysical Research: Oceans

Future ocean acidification in the Canada Basin and surrounding Arctic Ocean from CMIP5 earth system models

Authors

  • N. S. Steiner,

    Corresponding author
    1. Fisheries and Oceans Canada, Institute of Ocean Sciences and Canadian Centre for Climate Modelling and Analysis, Sidney, British Columbia, Canada
    • Corresponding author: N. S. Steiner, Fisheries and Oceans Canada, Institute of Ocean Sciences and Canadian Centre for Climate Modelling and Analysis, PO Box 6000, 9860 West Saanich Rd., Sidney, BC V8L 4B2, Canada. (Nadja.Steiner@ec.gc.ca)

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  • J. R. Christian,

    1. Fisheries and Oceans Canada, Institute of Ocean Sciences and Canadian Centre for Climate Modelling and Analysis, Sidney, British Columbia, Canada
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  • K. D. Six,

    1. Department of The Ocean and The Earth System, Max Planck Institute for Meteorology, Hamburg, Germany
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  • A. Yamamoto,

    1. Division of Climate System Research, University of Tokyo, Chiba, Japan
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  • M. Yamamoto-Kawai

    1. Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
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Abstract

[1] Six Earth system models that include an interactive carbon cycle and have contributed results to the 5th Coupled Model Intercomparison Project (CMIP5) are evaluated with respect to Arctic Ocean acidification. Projections under Representative Concentration Pathways (RCPs) 8.5 and 4.5 consistently show reductions in the bidecadal mean surface pH from about 8.1 in 1986–2005 to 7.7/7.9 by 2066–2085 in the Canada Basin, closely linked to reductions in the calcium carbonate saturation state ΩA,C from about 1.4 (2.0) to 0.7 (1.0) for aragonite (calcite) for RCP8.5. The large but opposite effects of dilution and biological drawdown of DIC and dilution of alkalinity lead to a small seasonal amplitude change in Ω, as well as intermodel differences in the timing and sign of the summer minimum. The Canada Basin shows a characteristic layering in Ω: affected by ice melt and inflowing Pacific water, shallow undersaturated layers form at the surface and subsurface, creating a shallow saturation horizon which expands from the surface downward. This is in addition to the globally observed deep saturation horizon which is continuously expanding upward with increasing CO2 uptake. The Eurasian Basin becomes undersaturated much later than the rest of the Arctic. These CMIP5 model results strengthen earlier findings, although large intermodel differences remain: Below 200 m ΩA varies by up to 1.0 in the Canada Basin and the deep saturation horizon varies from 2000 to 4000 m among the models. Differences of projected acidification changes are primarily related to sea ice retreat and responses of wind mixing and stratification.

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