Arctic amplification fingerprints on the midlatitude circulation in a medium-complexity global atmospheric model

Abstract

Arctic amplification is a key feature of recent climate change, yet the relative roles of sea surface temperature (SST) and sea ice cover (SIC) changes remain debated. Using an intermediate-complexity atmospheric model, we isolate their individual and combined impacts through a set of atmosphere-only experiments. Results show that SST changes dominate warming at low and midlatitudes, while SIC loss controls Arctic warming. These forcings produce distinct circulation responses, with SST driving a poleward jet shift and SIC inducing opposite changes. When combined, their interaction leads to a reduced and less robust atmospheric response. Neither forcing alone reproduces the observed magnitude of polar amplification: SIC-only experiments overestimate it, while SST-only simulations underestimate it. A realistic representation emerges only when both are included, highlighting their complementary roles. These findings provide a physical framework to interpret polar amplification as the combined effect of global and regional processes, with implications for understanding future Arctic change and its influence on midlatitude climate. At the same time, it highlights the utility of medium-complexity models to better understand physical mechanisms.