Glacier elevation changes in the Karakoram Range derived from TanDEM-X and SRTM/X-SAR digital elevation models, 2000-2012, link to GeoTIFF

Snow cover and glaciers in the Karakoram region are important freshwater resources for many down-river communities as they provide water for irrigation and hydropower. A better understanding of current glacier changes is hence an important informational baseline. We present glacier elevation changes in the central Karakoram region using TanDEM-X and SRTM/X-SAR DEM differences between 2000 and 2012. We calculated elevation differences for glaciers with advancing and stable termini or surge-type glaciers separately using an inventory from a previous study. Glaciers with stable and advancing termini since the 1970s showed nearly balanced elevation changes of -0.09 ± 0.12 m/a on average or mass budgets of -0.01 ± 0.02 Gt/a (using a density of 850 kg/m**3). Our findings are in accordance with previous studies indicating stable or only slightly negative glacier mass balances during recent years in the Karakoram. The high-resolution elevation changes revealed distinct patterns of mass relocation at glacier surfaces during active surge cycles. The formation of kinematic waves at quiescent surge-type glaciers could be observed and points towards future active surge behaviour. Our study reveals the potential of the TanDEM-X mission to estimate geodetic glacier mass balances, but also points to still existing uncertainties induced by the geodetic method.

喀喇昆仑地区的积雪与冰川是流域下游诸多社区的关键淡水资源，可为农业灌溉与水力发电提供用水支撑。因此，深入明晰当前冰川变化情况，乃是一项重要的基础信息基准。本研究基于2000年至2012年间TanDEM-X与SRTM/X-SAR数字高程模型（Digital Elevation Model, DEM）的差分数据，呈现喀喇昆仑中部区域的冰川高程变化特征。本研究依托既往研究的冰川编目数据，分别针对冰舌前进型、稳定型冰川以及跃动型冰川（surge-type glacier）计算了其高程差值。自20世纪70年代以来冰舌保持稳定或前进的冰川，其高程变化平均为-0.09±0.12米/年，近乎处于平衡状态；对应的物质平衡则为-0.01±0.02吉吨/年（计算采用冰密度850 kg/m³）。本研究结果与既往研究结论一致，即喀喇昆仑地区近年的冰川物质平衡处于稳定状态，仅存在轻微负值。高分辨率的高程变化数据揭示了活跃跃动周期内冰川表面物质再分布的显著特征模式。研究还观测到休眠跃动型冰川（quiescent surge-type glacier）上运动波（kinematic wave）的形成过程，这预示着该类冰川未来或将进入活跃跃动阶段。本研究证实了TanDEM-X任务在大地测量法冰川物质平衡估算方面的应用潜力，同时也指出了该大地测量方法仍存在的不确定性。