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...位于西格陵兰的雅各布港冰川（Jakobshavn Isbræ）其冰量等效于海平面上升0.6米，自20世纪90年代末以来一直在加速流动并退缩。此前，利用机载雷达测深仪测量其冰厚存在困难，这阻碍了对该冰川退缩机制的解析。本研究采用2012年获取的高分辨率直升机载重力数据，结合近海峡湾水深数据与内陆质量守恒算法作为约束条件，通过三维反演方法重建了该冰川洋缘50千米范围内的床面高程。研究发现，该冰川槽谷呈不对称形态，其下段的深度较此前估算值深达数百米。1996年至2016年间，该冰川的接地线以每年0.6千米的速度向深海迁移，深度从700米增至1100米。向上游方向，床面在10千米范围内骤降至1600米深度，随后在40千米范围内缓慢抬升至1200米深度。雅各布港冰川未来数十年内将沿逆向斜坡持续退缩。作者：An L.、E. 里尼奥特、S.H.P. 埃利夫、M. 莫里勒姆、R. 米利安、J. 穆吉诺、D.M. 霍兰等