Deglacial Pulse of Neutralized Carbon From the Pacific Seafloor: A Natural Analog for Ocean Alkalinity Enhancement?

Abstract The ocean carbon reservoir controls atmospheric carbon dioxide (CO 2 ) on millennial timescales. Radiocarbon ( 14 C) anomalies in eastern North Pacific sediments suggest a significant release of geologic 14 C‐free carbon at the end of the last ice age but without evidence of ocean acidification. Using inverse carbon cycle modeling optimized with reconstructed atmospheric CO 2 and 14 C/C, we develop first‐order constraints on geologic carbon and alkalinity release over the last 17.5 thousand years. We construct scenarios allowing the release of 850–2,400 Pg C, with a maximum release rate of 1.3 Pg C yr −1 , all of which require an approximate equimolar alkalinity release. These neutralized carbon addition scenarios have minimal impacts on the simulated marine carbon cycle and atmospheric CO 2 , thereby demonstrating safe and effective ocean carbon storage. This deglacial phenomenon could serve as a natural analog to the successful implementation of gigaton‐scale ocean alkalinity enhancement, a promising marine carbon dioxide removal method.