The role of sea ice in present and future Arctic amplification

The importance of sea-ice loss on the Arctic amplification of near-surface warming remains contentious, as Arctic amplification emerges even in model experiments with disabled surface-albedo feedback. Here we show that the characteristics and underlying dynamics of Arctic amplification may change greatly in a future ice-free climate using a series of climate model experiments. Our analysis indicates that although Arctic amplification continues over the 22nd century, it weakens markedly with a less distinct seasonality in a future ice-free climate. These changes are found to occur because the strength and seasonality of Arctic amplification in the current climate are attributed mainly to a tight coupling between cold-season lapse-rate feedback and sunlit-season surface-albedo feedback. The substantial differences in the characteristics of simulated Arctic amplification between the current and future ice-free climate therefore suggest that the presence of Arctic sea ice is an essential component of the current Arctic amplification regime. Arctic amplification persists even in a year-round sea ice-free state due to greenhouse gas forcing, but weakens in a future year-round sea ice-free climate, implying Arctic sea ice’s importance, according to analysis of climate model simulations.