Calving Dynamics and the Potential Impact of Mélange Buttressing at the Western Calving Front of Thwaites Glacier, West Antarctica

IF 3.5 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Anna Crawford, Jan Åström, Douglas I. Benn, Adrian Luckman, Rupert Gladstone, Thomas Zwinger, Fredrik Robertsén, Suzanne Bevan
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Abstract

The western region of the wide Thwaites Glacier terminus is characterized by a near-vertical calving front. The grounding line at this western calving front (WCF) rests on a relatively high ridge, behind which exists a reverse-sloping bed; retreat of the grounding line into this over-deepening basin could therefore expose deep calving faces that may be subject to ice-cliff failure. Here, we use the 3D Helsinki Discrete Element Model to identify the factors that control the calving dynamics in this location. We then focus on the ability of mélange to influence these dynamics given the wide embayment in which Thwaites Glacier terminates. We find that calving along the WCF is currently influenced by ice flow across the grounding line and consequent longitudinal tensile stress and rift formation. Calving is slowed in simulations that are initiated with a highly constricted mélange, with a thicker mélange suppressing calving entirely. We liken the constrained simulations to a scenario in which mélange piles behind a large grounded iceberg. In a future which may see calving become a more dominant control on the retreat of Thwaites Glacier, this type of blockage will be necessary for robust force chains to develop and transmit resistive forces to the terminus. The ability of the mélange to hinder calving at this location will be determined by the presence and rigidity of binding land-fast sea ice and iceberg keel depths. Therefore, it is necessary to represent calving, mélange and sea ice in a single framework to predict the fate of Thwaites Glacier.

Abstract Image

南极洲西部 Thwaites 冰川西侧塌陷前沿的塌陷动态和融块加固的潜在影响
在宽阔的斯维斯冰川终点西部地区,有一个近乎垂直的冰川断裂前沿。西部冰川断裂前沿(WCF)的接地线位于一个相对较高的山脊上,山脊后面是一个反向倾斜的冰床;因此,接地线后退到这个过度加深的盆地可能会暴露出冰崖崩塌的深层断裂面。在此,我们使用赫尔辛基三维离散要素模型来确定控制该地点冰化动态的因素。然后,考虑到 Thwaites 冰川的终点位于宽阔的海湾中,我们将重点放在混杂岩影响这些动态的能力上。我们发现,目前沿 WCF 的断裂受冰流穿过接地线以及随之而来的纵向拉伸应力和裂缝形成的影响。在模拟开始时高度收缩的夹层中,钙化速度会减慢,而较厚的夹层则会完全抑制钙化。我们把受约束的模拟比作在大型搁浅冰山后面堆积褶皱的情景。在未来,冰崩可能会成为控制斯怀兹冰川退缩的一个更主要的因素,这种类型的阻塞对于形成强大的力链并将阻力传递到冰川末端是必要的。在这一位置,混杂层阻碍冰川断裂的能力将取决于结合陆地的海冰和冰山龙骨深度的存在和硬度。因此,有必要在一个单一的框架中表示出冰川断裂、海冰褶皱和海冰,以预测斯韦思冰川的命运。
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来源期刊
Journal of Geophysical Research: Earth Surface
Journal of Geophysical Research: Earth Surface Earth and Planetary Sciences-Earth-Surface Processes
CiteScore
6.30
自引率
10.30%
发文量
162
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