Assessing the potential of calcium-based artificial ocean alkalinization to mitigate rising atmospheric CO₂and ocean acidification

Abstract

[1] Enhancement of ocean alkalinity using calcium compounds, e.g., lime has been proposed to mitigate further increase of atmospheric CO 2 and ocean acidification due to anthropogenic CO 2 emissions. Using a global model, we show that such alkalinization has the potential to preserve pH and the saturation state of carbonate minerals at close to today's values. Effects of alkalinization persist after termination: Atmospheric CO 2 and pH do not return to unmitigated levels. Only scenarios in which large amounts of alkalinity (i.e., in a ratio of 2:1 with respect to emitted CO 2 ) are added over large ocean areas can boost oceanic CO 2 uptake sufficiently to avoid further ocean acidification on the global scale, thereby elevating some key biogeochemical parameters, e.g., pH significantly above preindustrial levels. Smaller-scale alkalinization could counteract ocean acidification on a subregional or even local scale, e.g., in upwelling systems. The decrease of atmospheric CO 2 would then be a small side effect. Citation: Ilyina, T., D. Wolf-Gladrow, G. Munhoven, and C. Heinze (2013), Assessing the potential of calcium-based artificial ocean alkalinization to mitigate rising atmospheric CO 2 and ocean acidification, Geophys. Res. Lett., 40,[5909][5910][5911][5912][5913][5914]

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

“…This is consistent with Kohler et al (2013) who saw little difference in adding olivine along existing shipping tracks, versus uniformly adding it to the surface ocean. It is also consistent with regional addition studies of Ilyina et al (2013), Feng et al (2016), and Feng et al (2017 which demonstrated a global impact.…”

“…In AOA_G there is little evidence of any of the very large increases in alkalinity seen in the more regional AOA experiments. This spatial pattern of relative increase is broadly consistent with the pattern of global alkalinity increase simulated by Ilyina et al (2013) and Keller et al (2014) for AOA in the (ice-free) global ocean.…”

“…They did not limit the amount of AOA, as their goal was to offset the projected future changes, and showed that the amount of AOA required to do this would drive the carbonate system to levels well above preindustrial levels. Ilyina et al (2013) also conclude that local AOA could potentially be used to offset the impacts of ocean acidification, with enhanced CO 2 uptake being only a side benefit. This regional approach was explored further by Feng et al (2016) who suggested that local AOA in the tropical ocean, in areas of high coral calcification, has the potential to offset the impacts of future rising atmospheric CO 2 levels under a high emissions scenario (RCP8.5).…”

“…Importantly, Kohler et al (2013) showed that the global effect of alkalinity added along shipping routes (as an analogue for practical implementation) was not significantly different from that of alkalinity added in a highly idealized uniform manner. Ilyina et al (2013) explored the potential of AOA to mitigate rising atmospheric CO 2 levels and ocean acidification in ocean-only biogeochemical simulations, and they showed that AOA has the potential to ameliorate future changes due to high CO 2 emissions. They did not limit the amount of AOA, as their goal was to offset the projected future changes, and showed that the amount of AOA required to do this would drive the carbonate system to levels well above preindustrial levels.…”

Research for assessment, not deployment, of Climate Engineering: The German Research Foundation's Priority Program SPP 1689

“…After termination of SRM, most of the carbon stored was quickly released back to the atmosphere, resulting from enhanced respiration in response to the rapid warming after termination known from earlier studies [Matthews and Caldeira, 2007]. Large-scale afforestation generated a substantial [Ilyina et al, 2013;Humpenöder et al, 2014Humpenöder et al, , 2015Moosdorf et al, 2014;Aswathy et al, 2015;Mengis et al, 2015Mengis et al, , 2016Saxler et al, 2015;Bonsch et al, 2016;Sonntag et al, 2016 in addition to references cited elsewhere in the paper], all provided in the reference list of this article.…”