Thaw slump inventory and TanDEM-X elevation loss rates (2015): Tuktoyaktuk coastlands, Canada, and Lena Delta area, Sakha Republic, Russia

Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of time scales. On sub-seasonal time scales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other drivers such as rainfall or the formation of an insulating veneer are also thought important. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellite (12 m resolution). The high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km²) allow us to track volume losses as drivers such as the available energy change during summer in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm/day) despite the ample available energy, indicating the widespread presence of an insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm/day), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August, respectively. The observed temporal patterns are poorly related to slump characteristics like the slump area. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.精准预测未来热融滑塌（thaw slump）活动，需深入理解不同时间尺度下控制块体运动（mass wasting）的大气驱动因子与地貌约束条件。在子季节尺度下，稀疏观测数据表明，活跃滑塌处的块体运动常受融冻所需能量限制，但降雨、隔热覆盖层形成等其他驱动因子也被认为具有重要影响。为研究子季节尺度驱动因子，本研究从TanDEM-X卫星（12米分辨率）获取的单航过雷达干涉测量数据中反演地形变化。该数据集具备高垂直精度（约30厘米）、高观测频次（重访周期约11天）与大范围覆盖（覆盖面积达5000平方千米）的优势，可支持我们在两个研究区域中，追踪夏季期间随可用能量等驱动因子变化的滑塌体体积损失过程。研究发现，加拿大图克托亚图克海岸带的热融滑塌在6月并未受能量限制：尽管可用能量充足，但滑塌体的块体运动强度极低（日均高度损失约0厘米），这表明区域内广泛存在积雪或碎屑隔热覆盖层。进入夏季中后期，高度损失速率普遍提升至约3厘米/天，但不同滑塌的变化模式存在显著差异。在诸多滑塌体中，块体运动强度随可用能量变化呈现同步时序特征，这一模式同样见于俄罗斯别科夫斯基半岛的沿海冰蕴永冻层（yedoma）崖壁。但其余两类常见时序变化轨迹则与可用能量变化不同步：一类对应强降水事件，另一类则在8月下旬出现速率突增。观测到的时序变化模式与滑塌面积等滑塌体特征的相关性极低。邻近热融滑塌之间迥异的时序行为特征，凸显出局地复杂且随时间变化的约束条件对块体运动的重要调控作用。