Wave Dispersion by Antarctic Pancake Ice from SAR images: a Method for Measuring Ice Thickness
Flavio Parmiggiani(1) , Peter Wadhams(2) , and Giacomo De Carolis(3)
via Gobetti 101,
(2) DAMTP Univ. of Cambridge , CMS Wilberford Road, CB3 0WB Cambridge, United Kingdom
(3) ISSIA-CNR, via Amendola 122, 70126 Bari, Italy
An ERS/SAR image of April 2000 over the advancing winter marginal ice zone (MIZ) in the Antarctic, which is composed of frazil-pancake ice, has been analysed. The aim was to test the predictions of a recently developed theory of wave dispersion in pancake ice which treats the ice as a viscous layer (Keller, 1998).
In the image, the structure of the wave spectrum in the MIZ and its change from the open-water spectrum (Wadhams et al., 2002) are consistent with a pancake layer 24 cm thick. Intensive in situ measurements of the pancake ice in the MIZ were carried on by FS Polarstern during a period covering the satellite imaging, some 280 km W of the image location. In situ measurements of mean ice thickness give thickness values very close to those obtained by SAR analysis.
This new technique is giving realistic results for ice thickness, while earlier works, based on a different dispersion theory (mass loading), tended to over-estimate ice thickness. We suggest that, after further validation, this SAR wave technique can become an accepted method for remotely sensing ice thickness in pancake icefields.
Keller, J. (1998). Gravity waves on ice-covered water. J. Geophys. Res,, 103, 7663-7669.
Wadhams, P., F. Parmiggiani and G. de Carolis (2002). The use of SAR to measure ocean wave dispersion in frazil-pancake icefields. J. Phys. Oceanogr., 32, 1721-1746.