Remotely sensed surface velocities, Lagrangian basal melt rates, terminus positions, grounding lines as well as modelling results of Peterman Glacier (northern Greenland)

This study assesses the response on ice dynamics of Petermann Glacier, a major outlet glacier in northern Greenland, to the 2012 and a possible future calving event. So far Petermann Glacier has been believed to be dynamically stable as another large calving event in 2010 had no significant impact on flow velocity or grounding line retreat. By analyzing a time series of remotely sensed surface velocities, we find an average acceleration of 10% between winter 2011/2012 and winter 2016/2017. This increase in surface velocity is not linear but can be separated into two parts, starting in 2012 and 2016 respectively. By conducting modelling experiments, we show that the first speed-up can be directly connected to the 2012 calving event, while the second speed-up is not captured. However, on recent remote sensing imagery newly developing fractures are clearly visible ~12,km upstream from the terminus, propagating from the eastern fjord wall to the center of the ice tongue, indicating a possible future calving event. By including these fracture zones as a new terminus position in the modelling domain we are able to reproduce the second speed-up, suggesting that surface velocities remain on the 2016/2017 level after the anticipated calving event. This indicates that, from a dynamical point of view, the terminus region has already detached from the main ice tongue.

本研究针对格陵兰北部主要入海冰川之一的彼得曼冰川（Petermann Glacier），探究其冰动力学对2012年冰崩事件（calving event）及未来潜在冰崩事件的响应。此前学界普遍认为彼得曼冰川处于动力学稳定状态，因为2010年发生的另一大型冰崩事件并未对其流速或接地线（grounding line）后退产生显著影响。通过分析遥感获取的表面流速时间序列数据，本研究发现2011/2012年冬季至2016/2017年冬季期间，冰川表面流速平均提升10%。该流速增幅并非线性变化，而是可划分为两个阶段，分别始于2012年与2016年。通过开展数值模拟实验，本研究证实第一阶段的流速加速可直接由2012年的冰崩事件引发，但第二阶段的加速未被现有模拟所复现。然而，在最新遥感影像中，距冰川终端约12千米的上游区域清晰可见新生成的裂隙，这些裂隙从东部峡湾岩壁向冰舌（ice tongue）中心延伸，预示着未来可能发生冰崩事件。将这些裂隙带作为模拟域内的新终端位置纳入模拟后，我们成功复现了第二阶段的流速加速，结果表明，在预期的冰崩事件发生后，冰川表面流速将维持在2016/2017年的水平。这表明，从动力学视角来看，冰川终端区域已与主冰舌发生脱离。