Abstract
AbstractHigh-resolution radar images of Glaciar Moreno, Argentina, acquired by the Shuttle Imaging Radar C (SIR-C) on 9 and 10 October 1994 at 24 cm wavelength (L-band), are utilized to map the glacier velocity both interferometrically and using the phase correlation method. The precision of the interferometric ice velocities is 1.8 cm d-1 (6 m a-1) (1σ). The phase correlation method measures ice velocity with a precision of 14 cm d-1 (50 m a-1) with image data at a 6 m sample spacing acquired 1 day apart. Averaged strain rates are measured with a precision of 10-4 d-1 at a 240 m sample spacing with the phase correlation method, and 10-5 d-l with radar interferometry. The phase correlation method is less precise than radar interferometry, but it performs better in areas of rapid flow, is more robust to temporal changes in glacier scattering and measures the glacier velocity in two dimensions with only one image pair. Using this technique, we find that Glaciar Moreno flows at 400 m a-1 in the terminal valley and 800 m a-1 at the calving front, in agreement with velocities recorded a decade ago. Assuming steady-state flow conditions, the vertical strain rates measured by SIR-C are combined with prior data on mass ablation to estimate the glacier thickness and ice discharge. The calculated discharge is 0.6 ± 0.2 km3 ice a-1 at 300 m elevation, and 1.1 ± 0.2 km3 ice a-1 at the equilibrium-line elevation (1150 m), which yields a balance accumulation of 6 ± 1 m ice a-1.
Highlights
Th e Patago ni a icefi elds a rc located at th e so uthwestern tip of South America a nd con sist of the north ern ice field (Hielo Patag6ni co l'\orte) a nd the so uth ern icefi eld (Hi elo Patag6nico Sur; HPS ) (Fig. 1)
In a reas of significant glacier 'v\feath ering a nd /o r deformation where ra dar interferometry is not always success ful, we propose a novel and complementa ry technique of da ta analysis for measuring ice velocity
To produce a n interferog ra m, the compl ex radar images a rc co-registered with sub-pi xel precisio n, a nd a raw in te rferog r a m is formed by co mputing the cross-product of the r egistered co mplex im ages
Summary
Th e Patago ni a icefi elds a rc located at th e so uthwestern tip of South America a nd con sist of the north ern ice field (Hielo Patag6ni co l'\orte) a nd the so uth ern icefi eld (Hi elo Patag6nico Sur; HPS ) (Fig. 1). In Ma rch and October 1994, the NASAlJet Propul sion L a boratory Shuttle Im aging R ada r C (SIR- C) provided th e first three-frequency, interferometric images of selec ted pa rts of th e ice fi eld s The sig na l amplitude may rema in correlated ove r long tim e p e ri ods, so the La ndsat technique is best used with image d a ta acquired over periods of months to yea rs, meaning la rge glacier di spl acem ents compared to th e pixel size. An example applic ati on of the phase correlation m ethod is prese nted here in th e case ofGlacia r Moreno, a m ~j o r outlet glacier of HPS, which was im aged repeatedly for interferometric applications in O ctobe r 1994 by SIR-C (Fig. I). Michel and R igllot: Flow qfelaciar M oreno r a nge/sin (34.37°)); a nd 5.21m in the a long-track or azimuth d i r ec ti on
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