Future Weakening of the ENSO Ocean Carbon Buffer Under Anthropogenic Forcing
Enhui Liao, Laure Resplandy, Junjie Liu, K. W. Bowman
Abstract
Abstract The El Niño Southern Oscillation (ENSO) is the largest driver of atmospheric CO 2 interannual variability. The equatorial Pacific Ocean, which is a natural source of CO 2 to the atmosphere, acts as a buffer of the terrestrial variations by releasing less CO 2 during El Niño events and releasing more CO 2 during La Niña events. Here, we examine how this ocean carbon buffer will respond to high anthropogenic emissions using Earth system models from Coupled Model Intercomparison Project Phase 6. The models project weaker ocean CO 2 flux anomalies in the future due to two main factors: a stronger compensation between thermal and nonthermal changes in ocean biogeochemistry (55% of signal) and a weaker influence of ENSO on the CO 2 transfer across the air‐sea interface (10%–25% of signal). The ocean would no longer buffer the land response to ENSO, and could even reinforce its impact on atmospheric CO 2 , amplifying the atmospheric carbon variability on interannual timescales.