SAR ANALYSIS OF THE TERRA NOVA BAY ICE EDDY OF SUMMER 2015

摘要

In the framework of a study of new-ice formation in Antarctica, SAR image acquisitions were planned over Terra Nova Bay (TNB). Thanks to the ESA Third Party Mission program, Cosmo-SkyMed and Radarsat-2 images were obtained for the period 20 February20 March, 2015; in addition, available Sentinel-1 images over TNB for the same period were retrieved from the ESA Scientific Data Hub. The first inspection of the images revealed the presence of a prominent eddy of surface ice, presumably induced by the wind blowing from the continent. Our first goal was to investigate the correlation between eddy area and wind field. Wind data were obtained from the AWS ‘Eneide’ located near the Italian Antarctic Base “Mario Zucchelli Station” at TNB. Formeasuring the eddy area, we developed a specific processing scheme which consists of the following stages: 1. Non-linear filtering; 2. Segmentation, based on the Markov Random Field theory, which uses a contextual approach applied to both the original and the filtered image; 3. Extraction of the eddy parameters, area and perimeter, by means of an active contour detection algorithm which works in an iterative way. The correlation between eddy area and wind field was analysed by means of the Running Correlation Coefficient function R_(cc) which can reveal the consistency between the two variables. R_(cc) attained high values in the period 20 February 12 March; after March 15, a powerful katabatic wind completely disrupted the surface ice eddy and displayed a well-defined polynya.