Avannarleq and Kujalleq Glacial Stability

The evolution of Greenland glaciers in a warming climate depends on their depth below sea level, flow speed, surface melt, and ocean-induced undercutting at the calving front. We present an innovative mapping of bed topography in the frontal regions of Sermeq Avannarleq and Kujalleq, two major glaciers flowing into the ice-choked Torssukatak Fjord, central west Greenland. The mapping combines a mass conservation algorithm inland, multi-beam echo sounding data in the fjord, and high-resolution airborne gravity data at the ice-ocean transition where other approaches fail. We obtain a reliable, precision (± 40 m) solution for bed topography across the ice-ocean boundary. The results reveal a 700-m deep fjord that abruptly ends on a 100-300 m deep sill along the calving fronts. The shallow sills explain the presence of stranded icebergs, the resilience of the glaciers to ocean-induced undercutting, and their remarkable stability over the past century. An. L., E. Rignot, J. Mouginot, R. Milan, (2018), A century of stability of Avannarleq and Kujalleq glaciers, West Greenland, explained using high-resolution airborne gravity and other data, Geophys. Res. Lett., 10.1002/2018GL077204.在气候变暖背景下，格陵兰冰川的演化进程取决于其水下埋藏深度、流动速率、表面消融强度，以及冰崩前沿（calving front）的海洋侧蚀作用。本研究针对格陵兰中西部注入被浮冰阻塞的托尔苏卡塔克峡湾的两大冰川——萨迈克·阿瓦纳勒克（Sermeq Avannarleq）与库亚莱克（Kujalleq）的峡湾前沿区域床层地形（bed topography）开展了创新性测绘工作。本次测绘融合了内陆区域的质量守恒算法（mass conservation algorithm）、峡湾内的多波束测深数据（multi-beam echo sounding data），以及在其他方法难以奏效的冰-洋过渡带（ice-ocean transition）获取的高分辨率航空重力数据（airborne gravity data）。我们得到了冰-洋边界区域床层地形的可靠高精度（±40米）解译结果。研究结果显示，该峡湾最大深度达700米，其末端在冰崩前沿处以100至300米深的海槛骤然截止。这类浅海槛可解释搁浅冰山的存在、冰川抵御海洋侧蚀的韧性，以及它们在过去一个世纪以来的显著稳定性。An. L.、E. Rignot、J. Mouginot、R. Milan（2018），《格陵兰西部阿瓦纳勒克与库亚莱克冰川百年稳定性——基于高分辨率航空重力及其他数据的解析》，《地球物理研究快报》（Geophys. Res. Lett.），10.1002/2018GL077204。