The deliberate large-scale manipulation of the Earth’s climate (geo-engineering) has been suggested for future interventions against climate change and ocean acidification. Geo-engineering techniques are generally grouped into two main types: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) methods. The former techniques aim at counteracting climate change by decreasing the incoming solar radiation reaching the Earth’s surface. The latter act upon the root of the problem by removing CO2 from the atmosphere. Thereby, CDR methods might also mitigate ocean acidification. Whilst the mitigation potential of the proposed technologies might sound promising, they also pose environmental threats. Lack of scientific assessment of side-effects and uncertainties leaves the door open for rogue projects to come in and potentially be dangerous and inefficient.

The core of our research is the ocean-based CDR method of alkalinity enhancement. Alkalinity characterizes the charge balance of ions in seawater and it determines the CO2 oceanic uptake and storage as well as the buffering capacity of the seawater to inhibit changes in pH. Ocean alkalinity might be artificially increased by, for instance, injecting the dissolution products of alkaline minerals into the seawater (e.g. calcium hydroxide or olivine). We conduct research on the multiple impacts of this method on the Earth system with the Max Planck Institute Earth System, providing information based on independent research to the geo-engineering scientific arena and to the policy-maker debate.

Based on a HAMOCC standalone version, we showed that alkalinization scenarios under which large amounts of alkalinity are released into the open ocean, the carbonate saturation state (omega) might reach levels under which inorganic precipitation of CaCO3 can occur (Ilyina ea, 2013). Furthermore, we show that despite an homogeneous addition of alkalinity over the ocean surface, pronounced differences in the seawater pH and omega response to alkalinization arise. Such different sensitivities of different ocean basins to alkalinity enhancement are due to emerging synergies between ocean thermal state, hydrodynamic regime, and changes in carbonate chemistry (Gonzalez ea, 2016).

Contact: Miriam Ferrer-Gonzalez

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González, M. F., and T. Ilyina (2016): Impacts of artificial ocean alkalinization on the carbon cycle and climate in Earth system simulations, Geophys. Res.Lett., 43, doi:10.1002/2016GL068576.