The Reversibility of Antarctic Sea Ice Loss Under CO ₂ Removal Scenarios

Abstract A pronounced decline in Antarctic sea ice has been observed since 2014, with major changes in the Earth system. This study investigates whether these impacts can be reversed by removing atmospheric greenhouse gases. Using carbon dioxide removal experiments from the Coupled Model Intercomparison Project Phase 6, we identify considerable inter‐model diversity in projections of Antarctic sea ice recovery, partly driven by a positive feedback loop starting from different initial ocean stratification in the present climate. Specifically, during the CO 2 increasing period, models with stronger initial stratification tend to store heat in the upper layer but not in the deeper layer in the Antarctic Ocean, accelerating sea ice melting, which in turn strengthens ocean stratification and thus impedes sea ice recovery during the CO 2 decreasing period. Conversely, weaker stratification promotes sea ice recovery under carbon dioxide removal scenarios. This demonstrates that the initial ocean stratification intensity exerts a critical influence on the reversibility of Antarctic sea ice loss.