Evaluation of remote-sensing techniques to measure decadal-scale changes of Hofsjökull ice cap, Iceland
Abstract:Dynamic surficial changes and changes in the position of the firn line and the areal extent of Hofsjökull ice cap, Iceland, were studied through analysis of a time series (1973–98) of synthetic-aperture radar (SAR) and Landsat data. A digital elevation model of Hofsjökull, which was constructed using SAR interferometry, was used to plot the SAR backscatter coefficient (°) vs elevation and air temperature along transects across the ice cap. Seasonal and daily ° patterns are caused by freezing or thawing of the ice-cap surface, and abrupt changes in ° are noted when the air temperature ranges from ∼−5° to 0°C. Late-summer 1997 ° (SAR) and reflectance (Landsat) boundaries agree and appear to be coincident with the firn line and a SAR ° boundary that can be seen in the January 1998 SAR image. In January 1994 through 1998, the elevation of this ° boundary on the ice capwas quite stable, ranging from 1000 to 1300 m, while the equilibrium-line altitude, as measured on the ground, varied considerably. Thus the equilibrium line may be obscured by firn from previous years. Techniques are established to measure long-term changes in the elevation of the firn line and changes in the position of the ice margin.
Document Type: Research Article
Publication date: June 1, 2000
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