Inter-hemispheric contrast in the sensitivity of polar amplification to sea-ice coverage conditions

Polar amplification of near-surface warming can have substantial global implications. However, large uncertainties remain regarding its future changes and the underlying mechanisms. Here we show substantial inter-hemispheric contrast in the climate state dependence of polar amplification by analyzing both future and distant past climates. Climate model simulations indicate that both the amplitude and seasonality of Arctic amplification greatly weaken in future sea ice-free climates. A similar feature is inferred from a paleoclimate data assimilation product. Yet, pronounced cloud-related uncertainties in summer-season Arctic amplification are found in distant past climate simulations. In comparison, the intensity and seasonality of Antarctic amplification are generally weaker and also less sensitive to the climate state in both future and distant past warm climates. Although cloud-related uncertainties in summer-season Arctic amplification need to be resolved, the overall agreement between future and distant past warm climates suggests that the inter-hemispheric contrast is likely to weaken as the Arctic approaches to sea ice-free climates. Arctic amplification is projected to weaken and lose seasonality in future sea ice-free climates, whereas Antarctic amplification will remain comparatively weaker and more stable, suggests a study combining distant past and future climate-model simulations with paleoclimate data assimilation.