Investigating the Role of Sea Ice Loss in Arctic Temperature Amplification

The Arctic surface has warmed much faster than lower latitudes during the satellite era, a phenomenon known as Arctic amplification (AA). Previous research has identified sea ice loss as a primary driver of AA, but the extent to which this loss contributes to observed Arctic warming remains unclear. Additionally, current reanalysis and atmospheric model simulations typically assume that sea ice thickness remains spatially constant over time. Compared to sea ice concentration loss, there have been fewer studies investigating the role of ice thinning in Arctic warming.

In this study, we use ensembles of simulations with the Community Atmosphere Model version 6 (CAM6) to investigate Arctic warming since 1980, exploring its connections to changes in sea ice concentration and thickness. We first demonstrate that the model, with all radiative and boundary forcings included, reasonably captures the observed Arctic warming and its seasonality. The warming signal largely disappears when the Arctic boundary forcing is replaced by seasonal climatology. Moreover, simulations driven solely by sea ice concentration loss reveal a significant portion of the total Arctic warming, and a majority (57.6%) of the amplified Arctic warming. Without sea ice loss, the relative warming between the Arctic and the global mean becomes much smaller. Furthermore, we found that sea ice thinning also contributes significantly to Arctic warming, particularly in the boreal winter and spring. Notably, the warming induced by ice thinning in the spring can potentially double the warming effect due to ice concentration loss. The warming from ice thinning is also spatially distinct from that caused by ice concentration loss. Collectively, these results highlight the important roles of sea ice concentration loss and ice thinning in observed Arctic warming.