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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 24 | Copyright

Special issue: Progress in quantifying ocean biogeochemistry – in honour...

Biogeosciences, 14, 5675-5691, 2017
https://doi.org/10.5194/bg-14-5675-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Dec 2017

Research article | 20 Dec 2017

Climate engineering and the ocean: effects on biogeochemistry and primary production

Siv K. Lauvset1, Jerry Tjiputra1, and Helene Muri2 Siv K. Lauvset et al.
  • 1Uni Research Climate, Bjerknes Centre for Climate Research, Jahnebakken 5, Bergen, Norway
  • 2Department of Geosciences, Section for Meteorology and Oceanography, University of Oslo, Oslo, Norway

Abstract. Here we use an Earth system model with interactive biogeochemistry to project future ocean biogeochemistry impacts from the large-scale deployment of three different radiation management (RM) climate engineering (also known as geoengineering) methods: stratospheric aerosol injection (SAI), marine sky brightening (MSB), and cirrus cloud thinning (CCT). We apply RM such that the change in radiative forcing in the RCP8.5 emission scenario is reduced to the change in radiative forcing in the RCP4.5 scenario. The resulting global mean sea surface temperatures in the RM experiments are comparable to those in RCP4.5, but there are regional differences. The forcing from MSB, for example, is applied over the oceans, so the cooling of the ocean is in some regions stronger for this method of RM than for the others. Changes in ocean net primary production (NPP) are much more variable, but SAI and MSB give a global decrease comparable to RCP4.5 (∼6% in 2100 relative to 1971–2000), while CCT gives a much smaller global decrease of ∼3%. Depending on the RM methods, the spatially inhomogeneous changes in ocean NPP are related to the simulated spatial change in the NPP drivers (incoming radiation, temperature, availability of nutrients, and phytoplankton biomass) but mostly dominated by the circulation changes. In general, the SAI- and MSB-induced changes are largest in the low latitudes, while the CCT-induced changes tend to be the weakest of the three. The results of this work underscore the complexity of climate impacts on NPP and highlight the fact that changes are driven by an integrated effect of multiple environmental drivers, which all change in different ways. These results stress the uncertain changes to ocean productivity in the future and advocate caution at any deliberate attempt at large-scale perturbation of the Earth system.

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Solar radiation management (SRM) is suggested as a method to offset global warming and to buy time to reduce emissions. Here we use an Earth system model to project the impact of SRM on future ocean biogeochemistry. This work underscores the complexity of climate impacts on ocean primary production and highlights the fact that changes are driven by an integrated effect of many environmental drivers, which all change in different ways.
Solar radiation management (SRM) is suggested as a method to offset global warming and to buy...
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