Grounding line remote operated vehicle (GROV) exploration of the ice shelf cavity of Petermann Glacier, Greenland

The melting of ice by ocean waters along the periphery of ice sheets is a major physical process driving their evolution in a warming climate. Using the fiber-optic-tethered Grounding line Remote Operated Vehicle (GROV), we explored the ice shelf cavity of Petermann Glacier, in Northwestern Greenland, in May 2023, using a novel interferometric multibeam sonar operating at 117 KHz with 360° viewing capability. The seafloor depth is uniform at 820 m and 200 m deeper than anticipated. At the ice shelf base, we find a succession of terraces interrupted by 20-40 m ice cliffs that have no signature at the surface, but are consistent with double-diffusive convection. The central melt channel deviates by ± 80 m from flotation, is smoother than indicated by the surface, and reveals asymmetric melt. The results demonstrate the fundamental importance of surveying the geometry of ice shelf cavities to document ice-ocean interaction.

气候变暖背景下，沿岸海水对冰盖外围冰体的消融是驱动冰盖演化的核心物理过程之一。2023年5月，我们借助光纤系留接地线遥控潜水器（Grounding line Remote Operated Vehicle, GROV），搭载工作频率为117 kHz、具备360°环视能力的新型干涉多波束声呐（interferometric multibeam sonar），对格陵兰西北部的彼得曼冰川（Petermann Glacier）冰架腔体开展了探测作业。本次探测测得海底地形深度均为820米，较预期值深200米。在冰架底部，我们观测到一系列阶地地貌，此类阶地被20至40米高的冰崖所截断；这类冰崖在冰架表面无对应地貌痕迹，但其形成与双扩散对流（double-diffusive convection）的作用结果一致。中央融水通道偏离漂浮平衡状态±80米，其地形相较于冰架表面更为平滑，且呈现出不对称的消融特征。本研究结果证实，对冰架腔体几何形态开展探测对于研究冰-海洋相互作用具有根本性的重要意义。