Reemergence of Anthropogenic Carbon Into the Ocean's Mixed Layer Strongly Amplifies Transient Climate Sensitivity
Keith B. Rodgers, Sarah Schlunegger, Richard D. Slater, Masao Ishii, Thomas L. Frölicher, Katsuya Toyama, Yves Plancherel, Olivier Aumont, Andrea J. Fassbender
Abstract
Abstract A positive marine chemistry‐climate feedback was originally proposed by Revelle and Suess (1957, https://doi.org/10.3402/tellusa.v9i1.9075 ), whereby the invasion flux of anthropogenic carbon into the ocean serves to inhibit future marine CO 2 uptake through reductions to the buffering capacity of surface seawater. Here we use an ocean circulation‐carbon cycle model to identify an upper limit on the impact of reemergence of anthropogenic carbon into the ocean's mixed layer on the cumulative airborne fraction of CO 2 in the atmosphere. We find under an RCP8.5 emissions pathway (with steady circulation) that the cumulative airborne fraction of CO 2 has a sevenfold reduction by 2100 when the CO 2 buffering capacity of surface seawater is maintained at preindustrial levels. Our results indicate that the effect of reemergence of anthropogenic carbon into the mixed layer on the buffering capacity of CO 2 amplifies the transient climate sensitivity of the Earth system.