Summer Arctic sea ice character from satellite microwave data


  • F. D. Carsey


In situ microwave data for the microscale properties of sea ice are combined with satellite data on the macroscale properties to construct an interpretation method for satellite data on sea ice for the warm season. Scatterometer, or calibrated radar, data give information on ice surface conditions, and radiometer data give information on areal concentrations of ponds and leads. The pond data are determined by examining fractional areas of exposed ice and using parameterized lead areas. These results are used to develop diffuse-illumination surface albedo estimates for the time of maximum ponding, near day 195, and that of minimum ice cover, near day 258. The estimated ponding albedos range from 0.5 to 0.6, and ice cover minimum albedos range from 0.6 to 0.8. During summer, the 37-GHz radiometer data are nearly independent of sea ice properties and are dominated by atmospheric and snow cover conditions. Lower-frequency data are increasingly useful for interpreting ice conditions. Substantial anisotropy in backscatter is recorded in scatterometer data at 14 GHz, with surface resolution of 50 km showing 90° anisotropy in the 0.5–1 dB range. In Nimbus 5 and Seasat data, some variation in satellite-recorded microwave properties during the period between 195 and 258 cannot be directly interpreted but are thought to be due to weather.