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https://www.nature.com/articles/d41586-023-02032-7

Scientists are proposing to add silicate minerals and other antiacid minerals to generate alkalinity that will capture atmospheric CO2 and decrease ocean acidification according to the following reaction:

Several issues to fix before large-scale application of this technology are reported in this paper. In addition, the release of silicic acid may stimulate diatom productivity with unknown implications on the effect of reverse weathering in sediments, which may produce acidity, once the diatoms have settled to the seafloor. More work by other groups is underway to help diagnose this potential carbon capture mechanism.

Coral Microbiomes Offer Clues for Resilience and Conservation

Using coral reef data from 233 locations across the globe, this recent paper estimates that the net vertical reef accretion rate will decrease globally by 76, 149, and 156% between 2050 and 2100, depending on the emissions scenarios for representative concentration pathways (RCP) identified by the IPCC. These scenarios include RCP2.6 (warming limited to < 2 oC above pre-industrial temperatures), RCP4.5 (maintaining a 4.5W radiative forcing, a moderate scenario in which emissions peak by 2040, then decline), and RCP8.5 (emissions continue to rise throughout the 21st century).

These estimates indicate that the world’s coral reefs will likely not maintain their functional role without near-term stabilization of atmospheric CO2 emissions and will disappear before the end of the 21st century under RCP4.5 and RCP8.5 conditions.

These declines in accretion rates largely originate from reduced coral cover as a result of bleaching events rather than from the direct impacts of ocean warming or acidification.

Cornwall et al., 2022 Proc. Nat. Acad. Sci. 118(21), e2015265118 (https://doi.org/10.1073/pnas.2015265118)

Cooley SR, Ono CR, Melcer S and Roberson J (2016) Community-Level Actions that Can Address Ocean Acidification. Front. Mar. Sci. 2:128. https://doi.org/10.3389/fmars.2015.00128

“It is virtually certain that upper ocean stratification has increased since 1970 and that sea water pH has declined globally over the last 40 years, with human influence the main driver of the observed ocean acidification (virtually certain).”

“Ocean acidification and associated reductions in the saturation state of calcium carbonate – a constituent of skeletons or shells of a variety of marine organisms – is expected to increase in the 21st century under all emissions scenarios (high confidence). There is very high confidence that present day surface pH values are unprecedented for at least 26,000 years and current rates of pH change are unprecedented since at least that time. Over the past 2–3 decades, a pH decline in the ocean interior has been observed in all ocean basins (high confidence).”

Find the full AR6 Climate Change 2021 report at: https://www.ipcc.ch/report/ar6/wg1/