Bed conditions of Pine Island Glacier, West Antarctica
Bed conditions of Pine Island Glacier, West Antarctica
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DOI：
10.1002/2016jf004033
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发表时间：
2017-01-01
影响因子：
3.9
通讯作者：
Rosier, S. H. R.
中科院分区：
文献类型：
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作者：
Brisbourne, A. M.;Smith, A. M.;Rosier, S. H. R.
尽管南极洲90%的排放是通过其快速流动的冰流发生的，但我们预测未来冰盖响应的能力受到用于确定基底滑动的数值模式中对冰床条件的不良观测约束的限制。我们通过获取和分析一系列地震反射剖面来确定西南极洲松岛冰川（PIG）主干道和支流下方的基本条件，帮助解决了这一观测缺陷。地震剖面显示大规模沉积矿床。结合地震反射图像，测量的声阻抗值表明主干支流正下方的床层条件相对均匀，包括一个广泛的改造沉积层，最小厚度为1.50.4m。在一个缓慢移动的支流间区域下，一个73米厚的离散低孔隙度沉积层被成像。尽管有相当大的基底地形，但地震观测表明，在PIG下方普遍存在冰基till层，这需要高度移动的沉积物体来维持充足的供应。这些结果与用于反演基底剪切应力的现有冰盖模型相一致：如果目前限制流动的高摩擦区域（位于接地线的正上游）被突破，现有的上游基础条件将不会抑制PIG的进一步快速撤退。然而，由于退缩后的应力重组，床上压力状态的微小变化可能导致床不易变形，并且不太可能保持高冰流速率。
Although 90% of Antarctica's discharge occurs via its fast-flowing ice streams, our ability to project future ice sheet response has been limited by poor observational constraints on the ice-bed conditions used in numerical models to determine basal slip. We have helped address this observational deficit by acquiring and analyzing a series of seismic reflection profiles to determine basal conditions beneath the main trunk and tributaries of Pine Island Glacier (PIG), West Antarctica. Seismic profiles indicate large-scale sedimentary deposits. Combined with seismic reflection images, measured acoustic impedance values indicate relatively uniform bed conditions directly beneath the main trunk and tributaries, comprising a widespread reworked sediment layer with a dilated sediment lid of minimum thickness 1.50.4m. Beneath a slow-moving intertributary region, a discrete low-porosity sediment layer of 73m thickness is imaged. Despite considerable basal topography, seismic observations indicate that a till layer at the ice base is ubiquitous beneath PIG, which requires a highly mobile sediment body to maintain an abundant supply. These results are compatible with existing ice sheet models used to invert for basal shear stress: existing basal conditions upstream will not inhibit further rapid retreat of PIG if the high-friction region currently restraining flow, directly upstream of the grounding line, is breached. However, small changes in the pressure regime at the bed, as a result of stress reorganization following retreat, may result in a less-readily deformable bed and conditions which are less likely to maintain high ice-flow rates.