Jakobshavn Glacier Bed Elevation

Jakobshavn Isbræ, West Greenland, which holds a 0.6-m sea level volume equivalent, has been speeding up and retreating since the late 1990s. Interpretation of its retreat has been hindered by difficulties in measuring its ice thickness with airborne radar depth sounders. Here, we employ high-resolution, helicopter-borne gravity data from 2012 to reconstruct its bed elevation within 50 km of the ocean margin using a three-dimensional inversion constrained by fjord bathymetry data offshore and a mass conservation algorithm inland. We find the glacier trough to be asymmetric and several 100 m deeper than estimated previously in the lower part. From 1996-2016, the grounding line migrated at 0.6 km/yr from 700 m to 1,100 m depth. Upstream, the bed drops to 1,600 m over 10 km then slowly climbs to 1,200 m depth in 40 km. Jakobshavn Isbræ will continue to retreat along a retrograde slope for decades to come. An L., E. Rignot, S.H.P. Elieff, M. Morlighem, R. Millan, J. Mouginot, D.M. Holland, D. Holland, and J. Paden (2017), Bed elevation of Jakobshavn Isbræ, West Greenland, from high-resolution airborne gravity and other data, Geophys. Res. Lett., 44, doi:10.1002/2017GL073245.

西格陵兰的雅各布港冰川（Jakobshavn Isbræ）拥有可使海平面上升0.6米的等效冰量，自20世纪90年代末以来一直在加速流动并发生退缩。此前，由于难以通过机载雷达测深仪获取准确的冰厚数据，学界对该冰川退缩过程的解释一直存在阻碍。本文利用2012年获取的高分辨率直升机航空重力数据，结合近海峡湾水深数据与内陆质量守恒算法构建约束条件，通过三维反演方法重建了该冰川海洋边缘50公里范围内的床面高程。研究发现，该冰川槽谷呈不对称形态，其下游区域的深度较此前估算值深数百米。1996年至2016年间，该冰川的接地线以每年0.6公里的速度向海迁移，所处水深从700米升至1100米。向上游方向，床面在10公里范围内骤降至1600米，随后在40公里范围内缓慢抬升至1200米。雅各布港冰川未来数十年将沿逆向斜坡持续退缩。作者：L. E. Rignot、S.H.P. Elieff、M. Morlighem、R. Millan、J. Mouginot、D.M. Holland、D. Holland与J. Paden（2017），《基于高分辨率机载重力及其他数据的西格陵兰雅各布港冰川床面高程》，《地球物理研究通讯》，第44卷，doi:10.1002/2017GL073245。