Area and mass changes of Siachen Glacier (East Karakoram)

Here, we present a comprehensive assessment of Siachen Glacier (East Karakoram), in terms of its area and elevation change, velocity variations and mass budget, utilizing different satellite datasets including Landsat, Hexagon, Cartosat-I, Shuttle Radar Topography Mission, Envisat Advanced Synthetic Aperture Radar and Japanese Advanced Land Observing Satellite Phased Array-type L-band SAR. The total areal extent of Siachen Glacier did not change significantly between 1980 and 2014; however the exposed-ice area decreased during that period. The terminus of the glacier has experienced substantial downwasting (on average 30 m) over the period of 1999-2007, followed by a retreat of the transition between exposed and debris-covered ice by a distance of 1.3 km during the short span 2007-14. The spatial patterns of the elevation difference and velocity are heterogeneous over the large areal extent of Siachen Glacier. The average velocity of the entire glacier, as computed between 11 December 2008 and 26 January 2009, was 12.3 ± 0.4 cm d^-1, while those estimated separately for the accumulation and ablation regions were 9.7 ± 0.4 cm d^-1 and 20.4 ± 0.4 cm d^-1, respectively. The mass budget of Siachen Glacier is estimated to be -0.03 ± 0.21 m w.e. a^-1 for the period of 1999-2007.