Abstract. Atmospheric carbon dioxide (CO2) levels continue to rise, increasing the
risk of severe impacts on the Earth system, and on the ecosystem services
that it provides. Artificial ocean alkalinization (AOA) is capable of reducing
atmospheric CO2 concentrations and surface warming and addressing ocean
acidification. Here, we simulate global and regional responses to alkalinity
(ALK) addition (0.25 PmolALK yr−1) over the period 2020–2100
using the CSIRO-Mk3L-COAL Earth System Model, under high (Representative
Concentration Pathway 8.5; RCP8.5) and low (RCP2.6) emissions. While
regionally there are large changes in alkalinity associated with locations of
AOA, globally we see only a very weak dependence on where and when AOA is
applied. On a global scale, while we see that under RCP2.6 the carbon uptake
associated with AOA is only ∼ 60 % of the total, under RCP8.5 the
relative changes in temperature are larger, as are the changes in pH
(140 %) and aragonite saturation state (170 %). The simulations
reveal AOA is more effective under lower emissions, therefore the higher the
emissions the more AOA is required to achieve the same reduction in global
warming and ocean acidification. Finally, our simulated AOA for 2020–2100 in
the RCP2.6 scenario is capable of offsetting warming and ameliorating ocean
acidification increases at the global scale, but with highly variable
regional responses.