Mapping the Thickness of Pancake Ice Using Ocean Wave Dispersion in SAR Imagery
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During the early to midwinter period pancake ice is a major component of the Antarctic sea ice cover, occupying a belt extending 200-300 km from the outer ice edge with an area of about 6 million km2. Experience in the Arctic suggests that the sea ice thickness in this region can be mapped by monitoring the penetration of ocean waves into it. Spectral analysis of subscenes from ERS-2 synthetic aperture radar (SAR) images yields the wavelength and direction of the principal spectral component both outside and inside the ice cover. There is a change of wavelength at the ice edge associated with a change in the wave dispersion, which can be quantitatively related to the thickness of the ice. The analysis is complex because the true wave spectrum must be retrieved from the SAR spectrum, which involves an inversion technique requiring a “first-guess” spectrum. The analysis technique is described, and the wave theory which predicts the change in wavelength. Experience in the Chukchi Sea and especially in the Odden ice tongue in the Greenland Sea is reviewed. Preliminary data from the Ross Sea have been analysed, yielding principal wave components, but the ambient wavelength was too long for the effect of ice to be detectable. The next application will be to the outer ice edge, when midwinter data from this region are available at the end of the current season.
KeywordsSynthetic Aperture Radar Wave Spectrum Synthetic Aperture Radar Imagery Directional Wave Spectrum Synthetic Aperture Radar Spectrum
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- 1.Wadhams P, LangeMA, Ackley SF (1987) The ice thickness distribution across the Atlantic sector of the Antarctic Ocean in midwinter. J Geophys Res 92 (C13): 14535–14552Google Scholar
- 2.Lange MA, Ackley SF, Dieckmann GS, Eicken H, Wadhams P (1989) Development of sea ice in the Weddell Sea. Ann Glaciol 12: 92–96Google Scholar
- 3.Martin S, Kauffman P (1981) A field and laboratory study of wave damping by grease ice. J Glaciol 27 (96): 283–313Google Scholar
- 4.Zwally HJ, Comiso JC, Parkinson CL, Campbell WJ, Carsey FD, Gloersen P (1983) Antarctic Sea Ice 1973–1976: satellite passive-microwave observations. NASA, Washington, Report SP-459Google Scholar
- 7.Wadhams P (1986) The seasonal ice zone. In: Untersteiner N (ed.) The geophysics of sea ice. Plenum Press, New York, 825–991Google Scholar
- 8.Peters AS (1950) The effect of a floating mat on water waves. Communs. Pure Appl. Math 3: 319354Google Scholar
- 11.Shapiro A, Simpson LS (1953) The effect of a broken icefield on water waves. Trans Am Geophys U 34 (1): 36–42Google Scholar
- 16.Hasselmann K, Hasselmann S (1991) On the nonlinear mapping of an ocean wave spectrum into a synthetic aperture radar image spectrum and its inversion. J Geophys Res 96(C6):10, 713–10, 729Google Scholar
- 18.Wadhams P, Comiso JC, Prussen E, Wells S, Brandon M, Aldworth E, Viehoff T, Allegrino R, Crane DR (1996) The development of the Odden ice tongue in the Greenland Sea during winter 1993 from remote sensing and field observations. J Geophys Res 101(C8):18, 213–18, 235Google Scholar
- 19.Wadhams P, De Carolis G, Parmiggiani F, Tadross M (1997) Wave dispersion by frazil-pancake ice from SAR imagery. Proc. IGARSS’97, Singapore, Aug. 1997, 41–43Google Scholar
- 20.Wadhams P, Parmiggiani F, Tadross M (1995) Wave spectra of SAR imagery of the Odden Ice Tongue. Proc. IGARSS’95, Florence, July 1995, I, 630–633Google Scholar