References

Biogeosciences

1726-4189

Copernicus Publications

Göttingen, Germany

10.5194/bg-6-1603-2009

Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake

Oschlies

IFM-GEOMAR, Leibniz-Institut für Meereswissenschaften, Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany

11 08 2009

6 8 1603 1613

2009

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://bg.copernicus.org/articles/6/1603/2009/bg-6-1603-2009.html

The full text article is available as a PDF file from https://bg.copernicus.org/articles/6/1603/2009/bg-6-1603-2009.pdf

The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. The smaller efficiency of the oceanic carbon uptake under an interactive atmosphere is due to the back flux of CO2 that occurs when atmospheric CO2 is reduced. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively, for pCO2 sensitivities of the terrestrial carbon storage in the middle range of the C4MIP models (Friedlingstein et al., 2006). For such sensitivities, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization originates, on timescales longer than decades, not from the atmosphere but from the terrestrial biosphere.

References 1

Aumont, O. and Bopp, L.: Globalizing results from ocean in situ iron fertilization experiments, Global Biogeochem. Cy., 20, GB2017, https://doi.org/10.1029/2005GB002591, 2006.

Bopp, L., Kohfeld, K. E., Le Quéré, C., and Aumont, O.: Dust impact on marine biota and atmospheric CO2 during glacial periods, Paleoceanography, 18, 1046, https://doi.org/10.1029/2002PA000810, 2003.

Caspersen, J. P., Pacala, S. W., Jenkins, J. C., Hurtt, G. C., Moorcroft, P. R., and Birdsey, R. A.: Contributions of land-use history to carbon accumulation in U.S. forests, Science, 290(5494), 1148–1151, 2000.

Cox, P. M., Betts, R. A., Jones, C. D., Spall, S. A., and Totterdell, I. J.: Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model, Nature, 408, 184–187, 2000.

Duce, R. A., LaRoche, J., Altieri, K., et al.: Impacts of atmospheric anthropogenic nitrogen on the open ocean, Science, 320(5878), 893–897, 2008.

Engel, A., Delille, B., Jacquet, S., Riebesell, U., Rochelle-Newall, E., Terbrüggen, A., and Zondervan, I.: TEP and DOC production by Emiliania huxleyi exposed to different CO2 concentrations: A mesocosm experiment, Aquat. Microb. Ecol., 34, 93–104, 2004.

Friedlingstein, P., Cox, P., Betts, R., et al.: Climate-carbon cycle feedback analysis: Results from the C4MIP model intercomparison, J. Climate, 19, 3337–3353, 2006 .

Gnanadesikan, A., Sarmiento, J. L., and Slater, R. D.: Effects of patchy ocean fertilization on atmospheric carbon dioxide and biological production, Global Biogeochem. Cy., 17, 1050, https://doi.org/10.1029/2002GB001940, 2003.

Houghton, J. T., Meira Filho, L. G., Griggs, D. J., and Maskell, K.: Stabilization of atmospheric greenhouse gases: Physical, biological and socioeconomic implications, Intergovernmental Panel on Climate Change, World Meteorological Organization, Geneva, Technical Paper III, 1997.

Jin, X., Gruber, N., Frenzel, H., Doney, S. C., and McWilliams, J. C.: The impact on atmospheric CO2 of iron fertilization induced changes in the ocean's biological pump, Biogeosciences, 5, 385–406, 2008.

Kurz, K. D. and Maier-Reimer, E.: Iron fertilization of the austral ocean – the Hamburg model assessment, Global Biogeochem. Cy., 7, 229–244, 1993.

Lampitt, R. S., Achterberg, E. P., Anderson, T. R., Hughes, J. A., Iglesias-Rodriguez, M. D., Kelly-Gerreyn, B. A., Lucas, M., Popova, E. E., Sanders, R., Shepherd, J. G., Smythe-Wright, D., and Yool, A.: Ocean fertilization: a potential means of geoengineering?, Philos. T. Roy. Soc. A., 366(1882), 3919–3945, 2008.

Luo, Y., Hui, D., and Zhang, D.: Elevated CO2 stimulates net accumulations of carbon and nitrogen in land ecosystems: a meta-analysis, Ecology, 87, 53–63, 2006.

Moore, J. K., Doney, S. C., Lindsay, K., Mahowald, N., and Michaels, A. F.: Nitrogen fixation amplifies the ocean biogeochemical response to decadal timescale variations in mineral dust deposition, Tellus B, 58, 560–572, 2006.

Orr, J. C., Maier-Reimer, E., Mikolajewicz, U., Monfray, P., Sarmiento, J. L., Toggweiler, J. R., Taylor, N. K., Palmer, J., Gruber, N., Sabine, C. L., Le Quéré, C., Key, R. M., and Boutin, J.: Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models, Global Biogeochem. Cy., 15, 43–60, 2001.

Oschlies, A. and Kähler, P.: Biotic contribution to air-sea fluxes of CO2 and O2 and its relation to new production, export production, and net community production, Global Biogeochem. Cy., 18, GB1015, https://doi.org/10.1029/2003GB002094, 2004.

Oschlies, A., Schulz, K. G., Riebesell, U., and Schmittner, A.: Simulated 21st century's increase in oceanic suboxia by CO2-enhanced biological carbon export, Global Biogeochem. Cy., 22, GB4008, https://doi.org/10.1029/2007GB003147, 2008.

Riebesell, U., Schulz, K., Bellerby, R. G. J., Fritsche, P., Meyerhöfer, M., Neill, C., Nondal, G., Oschlies, A., Wohlers, J., and Zöllner, E.: Enhanced biological carbon consumption in a high CO2 ocean, Nature, 450, 545–548, 2007.

Riebesell, U., Zondervan, I., Rost, B., Tortell, P. D., Zeebe, R. E., and Morel, F. M. M.: Reduced calcification of marine plankton in response to increased atmospheric CO2, Nature, 407, 364–367, 2000.

Sarmiento, J. L. and Le Quéré, C.: Oceanic carbon dioxide uptake in a model of century-scale global warming, Science, 274, 1346–1350, 1996.

Sarmiento, J. L. and Orr, J. C.: Three dimensional simulations of the impact of Southern Ocean nutrient depletion on atmospheric CO2 and ocean chemistry, Limnol. Oceanogr., 36, 1928–1950, 1991.

Sarmiento, J. L., Slater, R., Dunne, J., and Gnanadesikan, A.: Small scale carbon mitigation by patch iron fertilization, in preparation, 2009.

Schmittner, A., Oschlies, A., Giraud, X., and Eby, M.: A global model of the marine ecosystem for multi-millennial simulations, Global Biogeochem. Cy., 19, GB3004, https://doi.org/10.1029/2004GB002283, 2005.

Schmittner, A., Oschlies, A., Matthews, H. D., and Galbraith, E. D.: Future changes in climate, ocean circulation, ecosystems and biogeochemical cycling simulated for a business-as-usual CO2 emission scenario until 4000 AD, Global Biogeochem. Cy., 22, GB1013, https://doi.org/10.1029/2007GB002953, 2008.

Schneider, B., Engel, A., and Schlitzer, R.: Effects of depth- and CO2-dependent C:N ratios of particulate organic matter (POM) on the marine carbon cycle, Global Biogeochem. Cy., 18, GB2015, https://doi.org/10.1029/2003GB002184, 2004.

Sokolov, A. P., Kicklighter, D. W., Melillo, J. M., Felzer, B. S., Schlosser, C. A., and Cronin, T. W.: Consequences of considering carbon-nitrogen interactions on the feedbacks between climate and the terrestrial carbon cycle, J. Climate, 21, 3776–3796, 2008.

Thornton, P. E., Lamarque, J.-F., Rosenbloom, N. A., and Mahowald, N. M.: Influence of carbon-nitrogen cycle coupling on land model response to CO2 fertilization and climate variability, Global Biogeochem. Cy., 21, GB4018, https://doi.org/10.1029/2006GB002868, 2007.

Volk, T. and Hoffert, M. I.: Ocean carbon pumps – Analysis of relative strengths and efficiencies in ocean-driven atmospheric CO2 changes, in: The Carbon Cycle and Atmospheric CO2: Natural Variations, Archean to Present, edited by: Sundquist, E. and Broecker, W., AGU Geophysical Monograph, Washington DC, 32, 99–110, 1985.

Weaver, A. J., Eby, M., Wiebe, E. C., et al.: The UVic earth system climate model: Model description, climatology, and applications to past, present and future climates, Atmos. Ocean, 39, 361–428, 2001.