Radar interferometry detection of hinge-line migration on Rutford Ice Stream and Carlson Inlet, Antarctica

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Abstract
Satellite synthetic aperture radar interferometry is employed to map the hinge-line position, or limit of tidal flexing, of Rutford Ice Stream (RIS) and Carlson Inlet (CI), Antarctica, and detect its horizontal migration between 1992 and 1996. The hinge-line position is mapped using a model fit from an elastic-beam theory. The rms noise of the model fit is 1-7 mm. The hinge-line position is located with a statistical noise of 30—50 m. Using this method, we find no hinge-line migration on RIS and CI. Only the southern flank of CI, which is stagnant (velocity 10-20 m a−1 vs 100 m a−1 in the main flow of CI), retreated 376 ±36 m in 4 years. The effect of changes in ocean tide is calculated to yield a 60 m advance of the hinge-line position in our data. Hence, the detected stationarity of the hinge-line positions suggests stable ice-thickness conditions at the hinge line, except for the southern flank of CI which may be thinning. A comparison of the ice discharge calculated at the grounding line of RIS (17±2 km3 ice a−1) and of CI (2.9 ±0.3 km3a−1) with mass input from the interior regions (20 ±3 km3 ice a−1 for RIS and 2.9 ±0.4 km3 a–1 for CI) suggests a balanced mass budget for CI, whereas RIS may have a slightly positive mass budget of 3±4 km3 ice a−1.