Relating bed character and subglacial morphology using seismic data from Thwaites Glacier, West Antarctica
Relating bed character and subglacial morphology using seismic data from Thwaites Glacier, West Antarctica
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使用南极洲西部思韦茨冰川的地震数据关联河床特征和冰下形态
DOI：
10.1016/j.epsl.2018.12.008
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发表时间：
2019
影响因子：
5.3
通讯作者：
Holschuh, Nicholas
中科院分区：
文献类型：
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作者：
Muto, Atsuhiro;Anandakrishnan, Sridhar;Alley, Richard B.;Horgan, Huw J.;Parizek, Byron R.;Koellner, Stephen;Christianson, Knut;Holschuh, Nicholas
对思韦茨冰川的地震测量显示了一个空间可变的河床特征，与冰盖稳定性的影响。南极西部冰盖正在通过阿蒙森海湾的出口冰川和冰流（包括思韦茨冰川）迅速失去质量，有限的观测和建模表明冰流速率取决于河床特性。在这里，我们表征床的性质的Thwaites冰川的反射地震数据的振幅分析的基础上收集的近似流动方向和两个100公里长的配置文件横向流动的100公里长的配置文件。地震剖面的上游部分揭示了一个1.12公里长的沉积盆地，冰流排列的床型被一个连续的冰碛层覆盖，冰碛层可能是柔软的和变形的（孔隙度为0.4-0.45），有几个地方的水汇集在床上。在沉积盆地的下游，河床上升了1.400米，超过1.25公里，进入冰下高地。我们对这些冰下高地的地震调查显示，在崎岖的地形上（振幅为200米，波长为102至5公里），类似于峭壁和尾巴，河床特征存在强烈的空间变化。地形高点的迎风面（面向冰川上游）冰碛物更加坚固（孔隙度为0.3-0.35或更低），而背风面（面向冰川下游）和平坦地区的孔隙度与上游沉积盆地的冰碛物相似。建模研究可以利用观测到的床特性和床面和坡度之间的相关性，将我们的观测扩展到思韦茨冰川的其他部分，从而得出未来接地线撤退的更现实的模型。我们的研究结果强调，需要更多的地球物理限制床属性在南极洲和格陵兰岛的重要出口。
Seismic measurements on Thwaites Glacier show a spatially variable bed character, with implications for ice-sheet stability. The West Antarctic Ice Sheet is losing mass rapidly through outlet glaciers and ice streams in the Amundsen Sea Embayment, including Thwaites Glacier, where limited observations and modeling suggest that ice-flow rates depend on bed properties. Here we characterize bed properties of Thwaites Glacier based on amplitude analysis of reflection-seismic data from a ∼40-km-long profile collected in the approximate flow direction and two ∼10-km-long profiles transverse to flow. The upstream portion of the seismic profile reveals a ∼12-km long sedimentary basin with ice-flow-aligned bedforms capped by a continuous till layer that is likely soft and deforming (porosity ∼0.4–0.45), with several locations where water has pooled at the bed. Downstream of the sedimentary basin, the bed rises by ∼400 m over ∼25 km into subglacial highlands. Our seismic survey of these subglacial highlands reveals strong spatial variations in bed character across rugged topography (∼200 m amplitude at ∼2- to 5-km wavelength) resembling crag-and-tails. Till on the stoss sides (facing upglacier) of topographic highs is more consolidated (porosity ∼0.3–0.35 or lower), whereas the lee sides (facing downglacier) and flat regions exhibit porosity similar to the till of the upstream sedimentary basin. Modeling studies could use the observed correlation between bed character and bed aspect and slope to extend our observations to other parts of Thwaites Glacier, resulting in more-realistic models of future grounding-line retreat. Our findings highlight the need for more geophysical constraints on bed properties for important outlets in Antarctica and Greenland.