Arctic amplification, and its seasonal migration, over a wide range of abrupt CO 2 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 CO 2 , and is caused by local and non-local mechanisms. In this study, we examine AA, and its seasonal cycle, in a sequence of abrupt CO 2 forcing experiments, spanning from 1 to 8 times pre-industrial CO 2 levels, using a state-of-the-art global climate model. We find that increasing CO 2 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 CO 2 levels. We further find that the seasonal peak in AA shifts gradually from November to January as CO 2 increases. Finally, we show that this seasonal shift in AA emerges in the 21st century in high-CO 2 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 CO 2 forcing in affecting the seasonal evolution of amplified Arctic warming, which carries important ecological and socio-economic implications.