| Volumes and Issues Contents of Issue 4 |
www.biogeosciences-discuss.net/6/7933/2009/
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Projected 21st century decrease in marine productivity: a multi-model analysis
1Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
2Oeschger Centre for Climate Change Research, University of Bern, Erlachstrasse 9a, 3012 Bern, Switzerland
3Laboratoire du Climat et de l'Environnement (LSCE), L'Orme des Merisiers Bât. 712, 91191 Gif sur Yvette, France
4Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1543, USA
5Institute of Geosciences, University of Kiel, Ludewig-Meyn-Str. 10, 24098 Kiel, Germany
6Max-Planck-Institut für Meteorologie, Bundesstrasse 53, 20146 Hamburg, Germany
Abstract. Changes in marine net primary productivity and export of particulate organic carbon are projected over the 21st century with three global coupled carbon cycle-climate models. These include representations of marine ecosystems and the carbon cycle of different structure and complexity. All three models show a decrease in global mean marine productivity and export production between 7 and 20% by 2100 relative to preindustrial conditions, for the SRES A2 emission scenario. Two different regimes for productivity changes are consistently identified in all three models. The first chain of mechanisms is dominant in the low- and mid-latitude ocean and in the North Atlantic: reduced input of macro-nutrients into the euphotic zone related to enhanced stratification, reduced mixed layer depth, and slowed circulation causes a decrease in macro-nutrient concentrations and in productivity and export of particulate organic carbon. The second regime is projected for parts of the Southern Ocean: an alleviation of light and/or temperature limitation leads to an increase in primary and export production as productivity is fueled by a sustained nutrient input. A region of disagreement among the models is the Arctic, where two models project an increase in productivity while one model projects a decrease. Projected changes in seasonal and interannual variability are modest in most regions. Regional model skill metrics are proposed to generate multi-model mean fields that show an improved skill in representing observations compared to a simple multi-model average. Model results are compared to recent productivity projections with three different algorithms, usually applied to infer primary production from satellite observations.
Discussion Paper (PDF, 4258 KB) Interactive Discussion (Closed, 4 Comments)
Citation: Steinacher, M., Joos, F., Frölicher, T. L., Bopp, L., Cadule, P., Doney, S. C., Gehlen, M., Schneider, B., and Segschneider, J.: Projected 21st century decrease in marine productivity: a multi-model analysis, Biogeosciences Discuss., 6, 7933-7981, 2009. Bibtex EndNote Reference Manager
