Tide deflection of Campbell Glacier Tongue, Antarctica, analyzed by double-differential SAR interferometry and finite element method

A glacier tongue, the terminus of a glacier projecting out from the coastline and floating over the ocean, experiences vertical deflection due to the fluctuation of ocean tide. Accurate analysis of the tidal deflection of a glacier tongue is necessary to understand the elastic properties and dynamics of glacial ice. We extracted the tidal deflection of Campbell Glacier Tongue (CGT), one of the fast-flowing glacier tongues in East Antarctica, by using 120 Double-Differential Interferometric SAR (DDInSAR) images from the 16 COSMO-SkyMed one-day tandem interferometric SAR image pairs obtained during 2010 and 2011. A map of tide deflection ratio (α-map), defined as the ratio of the tidal deflection over tide height, was generated by pixel-based linear regression between the DDInSAR-derived tidal deflection and the tidal variation predicted by various tide models such as TPXO7.1, FES2004, CATS2008a and Ross_Inv after the inverse barometer effect correction. We also generated the maps of R2, root mean square error (RMSE), and intercept (β) of the linear regression model. We confirmed that the horizontal flow of the Campbell Glacier is steady over the whole data acquisition period due to the fact that α values were close to zero over the grounded part of the glacier. Ross_Inv provided the most reliable α-map with the highest R2 (0.97) and the smallest RMSE (0.3 cm) beyond the hinge zone than other tide models. The spatial variation of the tidal response of the whole CGT was clearly defined from the α-map. The grounding line retreated by 0.3-1.5 km in comparison with that in 1996 defined by Rignot et al., 2011a. The ice thickness of CGT was estimated to be 397 ± 71 m from ICESat surface elevation data. The Young's modulus of CGT was found to be 0.5-1.3 GPa (0.8 GPa at an ice thickness of 397 m) by simulating the α in the hinge zone using a 2-dimensional finite element method.