Investigating the Arctic sea ice insulating effect with the GFDL-CM4 model

Arctic sea ice acts as an insulator and influences atmosphere-ocean heat exchange and, thus, the global climate. While sea ice extent and thickness exhibit a profound declining trend over the satellite area, the impact of sea ice thinning is quite underexplored. This study examines the insulative effect induced by the variations in sea ice thickness as well as effective thickness, which encompass both sea ice and snow layers. Using the GFDL-CM4 model, we analyze the historical trends and high-emission future projections in sea ice thickness, snow, conductive heat flux, and near-surface air temperature. Focusing on the winter season where the insulating effect of sea ice is expected to be the most manifested due to a weak-to-zero solar radiation and a high sea ice concentration, we found a ~66% drop (from 3.2 m to 1.0 m) in March effective thickness by 2100, with an emergence of the first September ice-free in 2060. This is accompanied by an increase of approximately 11 W m^-2 in conductive heat flux in March by the zero-layer thermodynamic model and about 7 ˚C increase in near-surface air temperature, indicating the reduced ice thickness increases the conductive heat through sea ice and further contributes to the near-surface warming in the Arctic. Further analyses of Arctic subdomain demonstrate regional variations, with the strongest insulating effects observed in the Kara and Barents Sea – regions that are also the first to experience ice-free conditions and a consequent diminishing of sea ice insulating effect. We will discuss how the findings presented here reinforce the existing community efforts, with an aim to catalyze further research into the impact of both sea ice and effective thickness and on the amplified Arctic warming.