Improved determination of the sea ice edge with SSM/I data for small-scale analyses

A method to derive the sea ice edges from the 37- and 85-GHz channels of the spaceborne Special Sensor Microwave/Imager (SSM/I) with higher resolution than operational ice concentration analyses is developed. A combined ice-atmosphere model to evaluate atmospheric influences showed that under clear sky conditions the error of the ice edge position is 3.1 km on average. The method performs well up to total liquid water content (TWC) of 125 g/m² and overestimates the ice extent when TWC increases up to 250 g/m². The algorithm is suitable to classify open water, the interior ice pack, and thin ice (nilas) or low ice concentrations caused by a mixture of open water and pancake ice. Simulations showed that interpolation and resolution-matching techniques may improve the retrieval results with emphasis on interpolation. Validation of the algorithm with high-resolution infrared data shows errors of the ice edge on average less than 5 km. Comparison with the NASA Team ice concentration algorithm in the Weddell Sea, Antarctica, shows best agreement with the contour line of 33% ice concentration. The suitability of the method for mesoscale investigations is demonstrated with a time series of a meander structure in the marginal ice zone (MIZ)