Arctic amplification, and its seasonal migration, over a wide range of abrupt CO2 forcing

Arctic amplification (AA), the larger warming of the Arctic compared to the rest of the planet, is widely attributed to the increasing concentrations of atmospheric CO2, and is caused by local and non-local mechanisms. In this study, we examine AA, and its seasonal cycle, in a sequence of abrupt CO2 forcing experiments, spanning from 1 to 8 times pre-industrial CO2 levels, using a state-of-the-art global climate model. We find that increasing CO2 concentrations give rise to stronger Arctic warming but weaker AA, owing to relatively weaker warming of the Arctic in comparison with the rest of the globe due to weaker sea-ice loss and atmosphere-ocean heat fluxes at higher CO2 levels. We further find that the seasonal peak in AA shifts gradually from November to January as CO2 increases. Finally, we show that this seasonal shift in AA emerges in the 21st century in high-CO2 emission scenario simulations. During the early-to-middle 21st century AA peaks in November–December but the peak shifts to December-January at the end of the century. Our findings highlight the role of CO2 forcing in affecting the seasonal evolution of amplified Arctic warming, which carries important ecological and socio-economic implications.