In:
Earth System Dynamics, Copernicus GmbH, Vol. 10, No. 4 ( 2019-11-07), p. 711-727
Abstract:
Abstract. We investigate the climate mitigation potential and collateral effects of direct injections of captured CO2 into the deep ocean as a possible means to close the gap between an intermediate CO2
emissions scenario and a specific temperature target, such as the
1.5 ∘C target aimed for by the Paris Agreement. For that purpose, a suite of approaches for controlling the amount of direct CO2
injections at 3000 m water depth are implemented in an Earth system model of intermediate complexity. Following the representative concentration pathway RCP4.5, which is a medium mitigation CO2 emissions scenario, cumulative CO2 injections required to meet the 1.5 ∘C climate goal are found to be 390 Gt C by the year 2100 and 1562 Gt C at the end of simulations, by the year 3020. The latter includes a cumulative leakage of 602 Gt C that needs to be reinjected in order to sustain the targeted global mean temperature. CaCO3 sediment and weathering feedbacks reduce the required CO2 injections that comply with the 1.5 ∘C target by about 13 % in 2100 and by about 11 % at the end of the simulation. With respect to the injection-related impacts we find that average pH values
in the surface ocean are increased by about 0.13 to 0.18 units, when
compared to the control run. In the model, this results in significant
increases in potential coral reef habitats, i.e., the volume of the global
upper ocean (0 to 130 m depth) with omega aragonite 〉 3.4 and ocean temperatures between 21 and 28 ∘C, compared to the control run. The potential benefits in the upper ocean come at the expense of strongly acidified water masses at depth, with maximum pH reductions of about −2.37 units, relative to preindustrial levels, in the vicinity of the injection sites. Overall, this study demonstrates that massive amounts of CO2 would need to be injected into the deep ocean in order
to reach and maintain the 1.5 ∘C climate target in a medium
mitigation scenario on a millennium timescale, and that there is a trade-off
between injection-related reductions in atmospheric CO2 levels
accompanied by reduced upper-ocean acidification and adverse effects on deep-ocean chemistry, particularly near the injection sites.
Type of Medium:
Online Resource
ISSN:
2190-4987
DOI:
10.5194/esd-10-711-2019
DOI:
10.5194/esd-10-711-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2578793-7
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