Classification of Sea Ice Summer Melt Features in High-Resolution IceBridge Imagery

High-resolution observations of melt ponds (MPs) across the Arctic are lacking, yet essential for understanding the sea ice energy budget and under-ice ecology. We present a pixel-based classification scheme to identify undeformed and deformed ice, open water, and light, medium, and dark MPs in images of sea ice undergoing melt. The scheme was applied to 0.1-m resolution Operation IceBridge Digital Mapping System imagery covering an area of similar to 4,000 km(2). Observations of both the unconsolidated, marginal ice zone of the Beaufort/Chukchi Seas (B/C Seas) and the consolidated, multiyear ice of the central Arctic (CA) were obtained. Sea ice concentration (SIC), melt pond fraction (MPF), and pond color fraction (PCF) were derived on a per-image basis. SIC averaged 69% in the B/C Seas and 90% in the CA. We find that both MPF and PCF are dependent on the ice type on which ponds form. MPF averaged 25% in the B/C Seas, where dark ponds dominated and had a PCF of 60%, compared to a PCF of 9% and 31%, for medium and light ponds, respectively. MPF averaged 14% in the CA, where the PCF of light ponds was 68%, compared with 16% for both medium and dark ponds. As the multiyear ice of the Arctic Ocean is replaced by a younger, more seasonal ice cover, our results suggest that MPF will increase, and MP color will darken. This would enhance the ice albedo feedback, exacerbating that already due to the multidecadal decline in summer ice extent. Plain Language Summary Detailed observations of summer melt features on Arctic sea ice are limited, yet essential for modeling and understanding summer sea ice processes. An algorithm was developed to classify ice, open water, and melt ponds in high-resolution NASA Operation IceBridge Digital Mapping System (DMS) imagery. More than 17,000 images over similar to 4,000 km(2) were analyzed. Sea ice concentration (SIC), melt pond fraction (MPF), and pond color fraction (PCF) were derived from the classified images. We compared results from two regions with distinct ice conditions: the unconsolidated marginal ice zone in the Beaufort and Chukchi (B/C) Seas, which consisted of predominantly first year ice, and the consolidated, predominantly multiyear ice pack of the central Arctic (CA) Ocean. In the B/C Seas, we found that the MPF is greater, SIC is lower, and ponds are darker than in the CA region. As the percentage of first year ice in the Arctic increases, our results suggest that the Arctic-wide MPF will increase, and pond color will darken. This will contribute to the positive ice-albedo feedback mechanism and has implications for modeling sea ice albedo.