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The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2016-125
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
01 Aug 2016
Review status
A revision of this discussion paper was accepted for the journal The Cryosphere (TC).
Signature of Arctic first-year ice melt pond fraction in X-band SAR imagery
Ane S. Fors1, Dmitry V. Divine2, Anthony P. Doulgeris1, Angelika H. H. Renner2,3, and Sebastian Gerland2 1Department of Physics and Technology, University of Tromsø − The Arctic University of Norway, 9037 Tromsø, Norway
2Norwegian Polar Institute, FRAM Centre, 9296 Tromsø, Norway
3Institute of Marine Research, 9294 Tromsø, Norway
Abstract. In this paper we investigate the potential of melt pond fraction retrieval from X-band polarimetric synthetic aperture radar (SAR) on drifting first-year sea ice. Melt pond fractions retrieved from a helicopter-borne camera system were compared to polarimetric features extracted from four dual polarimetric X-band SAR scenes, revealing significant relationships. The correlations were strongly dependent on wind speed and SAR incidence angle. Co-polarisation ratio was found to be the most promising SAR feature for melt pond fraction estimation at intermediate wind speeds (6.2 m/s), with a correlation coefficient of 0.46. At low wind speeds (0.6 m/s), this relation disappeared due to low backscatter from the melt ponds, and backscatter VV-polarisation intensity had the strongest relationship to melt pond fraction with a correlation coefficient of −0.53. From the results, an intermediate and a low-wind speed empirical model for melt pond fraction estimation were suggested and evaluated. The models gave good estimates of mean melt pond fraction for the full satellite scenes, deviating with less than 4 % from the airborne retrieved melt pond fractions in the investigated area. A smoothing window of 51 × 51 pixels gave the best reproduction of the width of the melt pond fraction distribution. A considerable part of the backscatter signal was below the noise floor at SAR incidence angles above ~ 40 degree, restricting the information gain from polarimetric features above this threshold. Compared to previous studies in C-band, limitations concerning wind speed and noise floor set stricter constraints on melt pond fraction retrieval in X-band. Despite this, our findings demonstrate new possibilities in melt pond fraction estimation from SAR, opening for expanded monitoring of melt ponds during melt season. In the next step, melt pond estimation from SAR may supplement surveillance from optical satellites, providing melt pond information to climate applications during cloudy conditions.

Citation: Fors, A. S., Divine, D. V., Doulgeris, A. P., Renner, A. H. H., and Gerland, S.: Signature of Arctic first-year ice melt pond fraction in X-band SAR imagery, The Cryosphere Discuss., doi:10.5194/tc-2016-125, in review, 2016.
Ane S. Fors et al.
Ane S. Fors et al.

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This paper investigates the signature of melt ponds in satellite borne synthetic aperture radar (SAR) imagery. The study shows that polarimetric X-band SAR can be used to extract melt pond fraction from drifting first-year sea ice, and discusses the influence of factors like wind speed, SAR incidence angle and instrument noise floor. Melt ponds strongly influence the Arctic sea ice energy budget, and the results imply prospective opportunities for expanded monitoring of melt ponds from space.
This paper investigates the signature of melt ponds in satellite borne synthetic aperture radar...
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