(Table 1) Accumulation and ice discharge of West Antarctic glaciers draining into the Amundsen Sea between 1974 and 2007

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.先进陆地观测卫星（Advanced Land Observation System, ALOS）搭载的相控阵合成孔径雷达（Phased-Array Synthetic-Aperture Radar, PALSAR）是一款工作于L波段（1.27 GHz）的雷达系统，可开展大陆尺度的冰盖运动干涉观测。本研究表明，相较于C波段（5.6 GHz）雷达数据，PALSAR数据能够获取精度更优的冰运动速率测量结果，这得益于其在积雪与粒雪层中更高的时间相干性。我们对比了2006年获取的西南极洲派恩岛湾的PALSAR流速数据与1974至2007年的流速观测序列。1996年至2007年间，松岛冰川流速提升42%，且其绝大部分冰原区域发生脱底；史密斯冰川流速增幅达83%，同样出现了脱底现象，二者的最大增速均记录于2007年。思韦茨冰川并未出现流速加快的情况，但其范围随时间持续扩张，且其东部冰架的流速翻倍。上述冰川的总冰通量在12年内增长30%，净质量损失从39±15吉吨每年升至105±27吉吨每年，增幅达170%。长期流速变化数据显示，该区域在20世纪70年代仅存在小幅质量损失。随着这些冰川向内陆更深、更平缓的床层区域脱底，未来该区域的质量损失规模将显著扩大。