Abstract
The Advanced Land Observation System (ALOS) Phased‐Array Synthetic‐Aperture Radar (PALSAR) is an L‐band frequency (1.27 GHz) radar capable of continental‐scale interferometric observations of ice sheet motion. Here, we show that PALSAR data yield excellent measurements of ice motion compared to C‐band (5.6 GHz) radar data because of greater temporal coherence over snow and firn. We compare PALSAR velocities from year 2006 in Pine Island Bay, West Antarctica with those spanning years 1974 to 2007. Between 1996 and 2007, Pine Island Glacier sped up 42% and ungrounded over most of its ice plain. Smith Glacier accelerated 83% and ungrounded as well. Their largest speed up are recorded in 2007. Thwaites Glacier is not accelerating but widening with time and its eastern ice shelf doubled its speed. Total ice discharge from these glaciers increased 30% in 12 yr and the net mass loss increased 170% from 39 ± 15 Gt/yr to 105 ± 27 Gt/yr. Longer‐term velocity changes suggest only a moderate loss in the 1970s. As the glaciers unground into the deeper, smoother beds inland, the mass loss from this region will grow considerably larger in years to come.
Highlights
[4] Here, we examine data collected by the Advanced Land Observation System (ALOS) Phased-array L-band Synthetic-Aperture Radar (PALSAR) L-band radar in 2006, six months after launch
We show results from the Amundsen Sea sector of West Antarctica and compare them with those obtained with Radarsat, ERS, and Landsat between 1974 and 2007
[15] Flow changes observed on Thwaites Glacier are different and confirm measurements from year 2000 [Rignot et al, 2002]: there is little to no acceleration at the center but a widening of the core of fast flow, accompanied by a doubling of the eastern ice-shelf velocity in 10 yr
Summary
[2] Synthetic-aperture radar interferometry (InSAR) has proven to be a valuable tool for measuring ice motion and grounding line position [e.g., Joughin et al, 1996; Rignot, 1996]. Most InSAR data collected to date have been acquired at the C-band frequency (5.6 GHz or 5.6 cm wavelength). Data collected at the L- and C-band frequencies by the Space Shuttle Experiment SIR-C in 1994, indicated that longer radar wavelengths offer superior temporal coherence on snow and ice surfaces because of their penetration into the snow and firn [Rignot et al, 1996, 2001; Dall et al, 2001]. Few satellite L-band InSAR data have been collected on glacier ice, and nearly none on ice sheets. We conclude with a discussion of the evolution of glaciers and mass balance in this region and their past and future impact on sea level rise
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