Sensitivity study of the effects of black carbon on Arctic sea ice using CICE sea-ice model

Black carbon (BC) is one of the most important absorbing particles in the atmosphere. BC can reduce the albedo of snow/ice and enhance the absorption of solar radiation at ultraviolet (UV) and visible wavelengths when it deposited on snow/ice surface. The deposition of BC can lead to an acceleration of the melting of snow/ice. To quantify the changing process of BC in snow/ice and its contribution to the melting of snow/ice, a series of sensitivity numerical experiments including the impacts of BC species (hydrophobic and hydrophilic), deposition rate, and scavenging efficiency of BC was completed using the Icepack one-dimensional column model of CICE. Further, we evaluate the effects of BC deposition on Arctic albedo and ice thickness, forced by ERA5 reanalysis data and BC deposition rate from CMIP6, including two simulation results of the historical experiments with GISS-E2 model and EC-Earth3 model. The results indicate that the hydrophobic BC can cause a reduction of snow/ice albedo by 0.43% in the melting season, which is 35% larger than hydrophilic BC with the same deposition rate. When only the hydrophilic BC was considered, the impact on scavenging efficiency halved to BC content in snow/ice is similar to double the deposition rate in the melting season. Additionally, the 2D model results indicate that the existence of BC in snow could enhance the absorption of solar radiation in the snow layer and reduce the transmittance of radiation to the ice layer, leading to a thicker ice thickness before the melting season. The thermodynamic impact of BC is more significant in the marginal ice zone than that in the central Arctic, especially from Barents Sea to Laptev Sea. In this paper, we quantify the effects of BC on the melting of Arctic snow and sea ice and discuss the problems of the parameterizations of BC’s effect. This may contribute to the improvement of the sea ice model.

Key words: Black carbon; CICE model; Sensitivity experiment; Scavenging efficiency; Albedo