12 Years of Area Variation by the Drygalski Ice Tongue as Measured With COSMO-SkyMed

Abstract

One important coastal polynya around Antarctica is Terra Nova Bay (TNB) polynya. Its formation and persistence are due to the combined effect of katabatic winds, regional ice conditions, and the Drygalski Ice Tongue (DIT). The combined effect of these elements arranges a delicate balance in Terra Nova Bay. To evaluate the interacting elements, we focused our attention on the Drygalski Ice Tongue, one of the largest ice tongues in Antarctica. The DIT is a 70-kilometre long tongue which juts out like a pier from the icy land into northern McMurdo Sound of Antarctica's Ross Dependency. The analysis presented in this paper was carried out using Cosmo-SkyMed (CSK) images. The methodology developed for the analysis consists of three steps: 1) DIT shape enhancement, 2) fuzzy Bayesian segmentation which associates the analysed set of pixels with a binary label field, and 3) parametric representation of the shape of the DIT to compare the area of the ice tongue as it was 12 years ago and as it is today. The computed mean value of the DIT surface velocity was 703 m y <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . To estimate the closeness of the derived parameter to the true value, using a statistical approach, the 95% confidence interval for the true mean value is 703±4.236 m y <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Our analysis confirms a trend of advance. That is, after the significant calving events of the tongue in 2005 and 2006, the DIT has resumed its normal growth, and its length has increased by 12% in the last 12 years.