Temporal variations in the flow velocity for Shirase Glacier in Antarctica over a 20-year period.

This paper presents that temporal variations in the flow velocity for Shirase Glacier in Antarctica were studied using synthetic aperture radar (SAR) images obtained by the Japanese Earth Resources Satellite-1 (JERS-1) in 1996-1998, the Advanced Land Observing Satellite (ALOS) in 2007-2010 and the ALOS-2 in 2014-2015. The scenes were analyzed using image correlation. The obtained ice-flow velocity increases rapidly from the upstream region to the coast, but its velocity is roughly constant over a region, 10 km long about the grounding line (GL), then gradually tends to increase again downstream from the GL. This trend has continued largely unchanged over the 20 years since 1996, judging from the flow velocity profiles obtained from JERS-l/SAR, ALOS/PALSAR and ALOS-2/PALSAR-2 observations. The flow velocity on the central streamline near the GL is 2.29 ± 0.02~0.03 km a^-1 (mean of 1996-2015). Between the GL and the point 30 km downstream, ice velocities tended to be lower in 2007-2010 or 2014-2015 than in 1996-1998. Upstream from the GL, the velocities were higher in 2007-2010 and 2014-2015 than in 1996-1998, increasingly so with distance upstream, reaching a maximum of approximately 0.57 km a^-1 (differences of mean velocity between 2007 and 2010) and 0.72 km a^-1 (differences of mean velocity between 2014 and 2015) at around 18 km upstream from the GL before decreasing again to a respective value of ~0.25 and ~0.35 km a^-1 at 30 km upstream. [ABSTRACT FROM AUTHOR]