Because of the limited measurements in physicochemical characteristics of the snowpack overlying Arctic sea ice,the evolution of the snowpack and its effect on black carbon (BC) migration is still unclear,especially in Arctic melt season.The characteristics of snowpack and contained BC are investigated in this study using the measurements performed during recent two Arctic cruises.Melt-freeze crust and icy layer were frequently observed in the melting snowpack in the cruise lines,demonstrating significant meltwater refreezing appearing in the historical evolution of the snowpack during melt season.The refreezing process may retain liquid meltwater or the scavenged BC within the snowpack that should have been flushed out to the ocean.Additionally,the icy layer is able to prevent the infiltration of the meltwater and some of the contained BC.Most of the BC content remained in Melt-freeze crust and icy layer was finally deposited to the surface scattering layer of the sea ice.This part of BC has not been considered in current sea ice models,which may be an important reason for model underestimation of BC in the melting snowpack overlying Arctic sea ice.