Measurement of all-wave and spectral albedos of snow-covered summer sea ice in the Ross Sea, Antartica

Abstract

All-wave albedo and spectral albedo data were collected over snow-covered pack-ice floes during summer 1999 (January and February) in the Ross Sea, Antarctica. Temporal variation of the all-wave albedo and spectral albedo was measured from the northern edge to the southern edge of the pack ice along three lines of longitude: 165° W, 150° W and 135° W. Snow depth, snow-cover stratification, snow-temperature profiles, and grain-size and morphology were also documented. It was observed that daily-averaged albedos were 0.70-0.86 for cloudy conditions over the pack ice. Only two sets of daily-averaged albedo were collected for clear-sky conditions (0.788 and 0.825). Albedo was lower at the marginal edges of the pack ice than in the central pack ice. Albedo was higher over the southern part of the central pack ice than over the northern part. Clear- and cloudy-sky albedos measured on the same site indicate that the average increase in albedo due to clouds is 1.4% (maximum 4.0%). Spectral albedos of the pack-ice floes were similar under clear-sky and cloudy conditions. Both are mainly controlled by the snow grain-size, especially in the top snow layer. All-wave albedos derived from measured visible and near-infrared spectral albedos, with extrapolation to ultraviolet and shortwave infrared regions for both clear- and cloudy-sky conditions, agreed well with all-wave albedos from direct measurements.