Articles | Volume 11, issue 23
Biogeosciences, 11, 6955–6967, 2014
Biogeosciences, 11, 6955–6967, 2014

Research article 11 Dec 2014

Research article | 11 Dec 2014

Projected pH reductions by 2100 might put deep North Atlantic biodiversity at risk

M. Gehlen1, R. Séférian2, D. O. B. Jones3, T. Roy4, R. Roth5, J. Barry6, L. Bopp1, S. C. Doney7, J. P. Dunne8, C. Heinze9,11,12, F. Joos5, J. C. Orr1, L. Resplandy1, J. Segschneider10, and J. Tjiputra11,12 M. Gehlen et al.
  • 1LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement, Orme des Merisiers, CEA/Saclay 91198 Gif-sur-Yvette Cedex, France
  • 2CNRM-GAME, Centre National de Recherche Météorologique-Groupe d'Etude de l'Atmosphère Météorologique, Météo-France/CNRS, 42 Avenue Gaspard Coriolis, 31100 Toulouse, France
  • 3National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
  • 4LOCEAN/IPSL, 4, place Jussieu 75252 PARIS Cedex 05, France
  • 5Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 6Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
  • 7Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • 8National Oceanic and Atmospheric Administration/Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08540, USA
  • 9Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, 5007 Bergen, Norway
  • 10Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany
  • 11Uni Research Climate, Bergen, Norway
  • 12Bjerknes Centre for Climate Research, Bergen, Norway

Abstract. This study aims to evaluate the potential for impacts of ocean acidification on North Atlantic deep-sea ecosystems in response to IPCC AR5 Representative Concentration Pathways (RCPs). Deep-sea biota is likely highly vulnerable to changes in seawater chemistry and sensitive to moderate excursions in pH. Here we show, from seven fully coupled Earth system models, that for three out of four RCPs over 17% of the seafloor area below 500 m depth in the North Atlantic sector will experience pH reductions exceeding −0.2 units by 2100. Increased stratification in response to climate change partially alleviates the impact of ocean acidification on deep benthic environments. We report on major pH reductions over the deep North Atlantic seafloor (depth >500 m) and at important deep-sea features, such as seamounts and canyons. By 2100, and under the high CO2 scenario RCP8.5, pH reductions exceeding −0.2 (−0.3) units are projected in close to 23% (~15%) of North Atlantic deep-sea canyons and ~8% (3%) of seamounts – including seamounts proposed as sites of marine protected areas. The spatial pattern of impacts reflects the depth of the pH perturbation and does not scale linearly with atmospheric CO2 concentration. Impacts may cause negative changes of the same magnitude or exceeding the current target of 10% of preservation of marine biomes set by the convention on biological diversity, implying that ocean acidification may offset benefits from conservation/management strategies relying on the regulation of resource exploitation.

Short summary
This study evaluates potential impacts of pH reductions on North Atlantic deep-sea ecosystems in response to latest IPCC scenarios.Multi-model projections of pH changes over the seafloor are analysed with reference to a critical threshold based on palaeo-oceanographic studies, contemporary observations and model results. By 2100 under the most severe IPCC CO2 scenario, pH reductions occur over ~23% of deep-sea canyons and ~8% of seamounts – including seamounts proposed as marine protected areas.
Final-revised paper