We use seismic refraction data to investigate the firn structure across a suture zone on the Amery Ice Shelf, East Antarctica, and the possible role of glacier dynamics in firn evolution. In the downstream direction, the data reveal decreasing compressional-wave velocities and increasing penetration depth of the propagating wave in the firn layer, consistent with $\sim$1 m firn thickening every 6 km. The boundary between the Lambert Glacier unit to the west and a major suture zone and the Mawson Escarpment Ice Stream unit to the east, is marked by differences in firn thicknesses, compressional-wave velocities and seismic anisotropy in the across-flow direction. The latter does not contradict the presence of a single-maximum crystal orientation fabric oriented 45–$90^{\circ }$ away from the flow direction. This is consistent with the presence of transverse simple shear governing the region's underlying ice flow regime, in association with elevated strain along the suture zone. The confirmation and quantification of the implied dynamic coupling between firn and the underlying ice requires integration of future seismic refraction, coring and modelling studies. Because firn is estimated to cover $\sim$98% of the Antarctic continent any such coupling may have widespread relevance to ice-sheet evolution and flow.

中文翻译：

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横跨南极洲东部艾默里冰架的复杂冰层结构的地震观测

我们使用地震折射数据来研究横跨南极洲东部埃默里冰架缝合带的冰层结构，以及冰川动力学在冰层演化中的可能作用。在下游方向，数据显示纵波速度降低，传播波在冰层中的穿透深度增加，与$\sim$每 6 km 就会有 1 m 的冰层增厚。西部的兰伯特冰川单元和一个主要的缝合带与东部的莫森悬崖冰流单元之间的边界以横流方向的冰层厚度、纵波速度和地震各向异性的差异为标志。后者不与单最大晶体取向织物的存在相矛盾 45-$90^{\circ}$远离流动方向。这与控制该地区潜在冰流状态的横向简单剪切的存在是一致的，与沿缝合区的应变升高有关。对冰层和下伏冰之间隐含的动态耦合的确认和量化需要整合未来的地震折射、取芯和建模研究。因为 firn 估计覆盖$\sim$98% 的南极大陆任何此类耦合都可能与冰盖演化和流动具有广泛的相关性。