Ocean-excited plate waves in the Ross and Pine Island Glacier ice shelves
Ocean-excited plate waves in the Ross and Pine Island Glacier ice shelves
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DOI：
10.1017/jog.2018.66
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发表时间：
2018-10-01
影响因子：
3.4
通讯作者：
Nyblade, Andrew A.
中科院分区：
文献类型：
--
作者：
Chen, Zhao;Bromirski, Peter D.;Nyblade, Andrew A.
冰架在支撑陆冰到达海洋，从而抑制陆冰流失的速度方面发挥着重要作用。长周期的重力波撞击会激发冰架的振动，从而扩大先前存在的裂缝，并引发冰山崩解。为了研究这些振动的空间振幅变化和传播特征，从2014年11月到2016年11月，在罗斯冰架(RIS)部署了34个台站的宽带地震台阵。两种类型的冰架板波被识别为波束形成：弯曲重力波和伸展兰姆波。在20 MHz以下，弯曲重力波主导着阵列上的相干信号，并以接近浅水重力波的速度(类似于S(-1)的70m)从冰锋向陆地传播。在20-100 MHz频段，伸展兰姆波占主导地位，其传播速度与S(-1)的3公里相速度相近。2012年1月至2013年12月，在松岛冰川(PIG)冰架上部署的5台宽带地震台阵也观测到了弯曲重力和伸展的Lamb波，在PIG上也检测到了20-100 MHz频段的弯曲波能量。考虑到南大洋无处不在的风暴活动，以及在RIS和猪冰架上的类似观测，很可能大多数(如果不是全部)南极西部冰架受到类似的重力波激励。
Ice shelves play an important role in buttressing land ice from reaching the sea, thus restraining the rate of grounded ice loss. Long-period gravity-wave impacts excite vibrations in ice shelves that can expand pre-existing fractures and trigger iceberg calving. To investigate the spatial amplitude variability and propagation characteristics of these vibrations, a 34-station broadband seismic array was deployed on the Ross Ice Shelf (RIS) from November 2014 to November 2016. Two types of ice-shelf plate waves were identified with beamforming: flexural-gravity waves and extensional Lamb waves. Below 20 mHz, flexural-gravity waves dominate coherent signals across the array and propagate landward from the ice front at close to shallow-water gravity-wave speeds (similar to 70 m s(-1)). In the 20-100 mHz band, extensional Lamb waves dominate and propagate at phase speeds similar to 3 km s(-1). Flexural-gravity and extensional Lamb waves were also observed by a 5-station broadband seismic array deployed on the Pine Island Glacier (PIG) ice shelf from January 2012 to December 2013, with flexural wave energy, also detected at the PIG in the 20-100 mHz band. Considering the ubiquitous presence of storm activity in the Southern Ocean and the similar observations at both the RIS and the PIG ice shelves, it is likely that most, if not all, West Antarctic ice shelves are subjected to similar gravity-wave excitation.