Comparing SHEBA and MOSAiC Observations of the Seasonal Evolution of Arctic Sea Ice Albedo

Abstract:

The albedo of the Arctic sea ice cover governs the surface radiative balance during the sunlit season and drives a variety of positive feedback mechanisms. It is known to be sensitive to the quantity and quality of snow, the formation and growth of melt ponds, and the presence of light-absorbing material (e.g., sediments, chlorophyll, soot, dust). Quantifying the seasonal evolution and physical drivers of albedo for pack ice has been a high priority for both field measurement campaigns and climate model development. Observations made 22 years ago during Ice Station SHEBA benchmarked the albedo evolution for a well-studied region of perennial sea ice. Recent observations from the 2020 MOSAiC summer have extended this record by documenting the albedo of an even more thoroughly-studied floe within the ‘new Arctic'. We compare and contrast the spectral and broadband observational records from these two campaigns. In particular, the duration of and transitions between various phases of melt evolution, the summer minimum, and effects of specific events including melt pond formation, drainage, and growth, episodic summer snowfall, condensation and precipitation, and the exposure of entrained sediment material resulting from surface ablation. While these two records are central to an empirical knowledge of the surface albedo evolution, they are snapshots in space of two ice covers with varying histories, forcings, geographical locations, and representativeness. We outline how the SHEBA and MOSAiC albedo records can be used together to promote next-generation albedo parameterizations that will need to increasingly move beyond empiricism to achieve generality, accuracy, consistency, and applicability to the future Arctic.