Thermal Weakening, Convergent Flow, and Vertical Heat Transport in the Northeast Greenland Ice Stream Shear Margins
Thermal Weakening, Convergent Flow, and Vertical Heat Transport in the Northeast Greenland Ice Stream Shear Margins
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DOI：
10.1029/2019gl083436
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发表时间：
2019-07-28
影响因子：
5.2
通讯作者：
Christianson, K.
中科院分区：
文献类型：
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作者：
Holschuh, N.;Lilien, D. A.;Christianson, K.
冰流的边界是速度的突变，称为切变裕度。一些剪切边缘是由冰下地形固定的，但另一些被认为是自组织的，通过控制冰盖应力平衡的冰粘性和基面阻力的热反馈而演变。阻力应力(和控制剪切边缘形成的特性)在表面上表现得不是唯一的，这促使使用地下观测来约束冰盖模型。在这项研究中，我们使用穿冰雷达资料对东北格陵兰冰流的三个三维热力模式进行了评估，重点是冰温(粘性的主要控制因素)和次表层速度的模式再现。数据/模型协议表明，格陵兰东北部冰流边缘的温度上升，东南边缘的深度平均温度比流动中的冰高2摄氏度至6摄氏度，这是由垂直热量输送而不是剪切加热驱动的。这项工作突出了停滞/流动转变过程中冰分歧的复杂性。
Ice streams are bounded by abrupt transitions in speed called shear margins. Some shear margins are fixed by subglacial topography, but others are thought to be self-organizing, evolving by thermal feedback to ice viscosity and basal drag which govern the stress balance of ice sheets. Resistive stresses (and properties governing shear-margin formation) manifest nonuniquely at the surface, motivating the use of subsurface observations to constrain ice sheet models. In this study, we use ice-penetrating radar data to evaluate three 3-D thermomechanical models of the Northeast Greenland Ice Stream, focusing on model reproductions of ice temperature (a primary control on viscosity) and subsurface velocity. Data/model agreement indicates elevated temperatures in the Northeast Greenland Ice Stream margins, with depth-averaged temperatures between 2 degrees C and 6 degrees C warmer in the southeast margin compared to ice in streaming flow, driven by vertical heat transport rather than shear heating. This work highlights complexity in ice divergence across stagnant/streaming transitions.