Collaborative Research: Dynamic Response of the Ross Ice Shelf to Wave-induced Vibrations

Bromirski/1246151该奖项支持一个项目，该项目旨在通过实地观测和数值模拟发现，如何使用海浪引起的冰架振动，特别是罗斯冰架（RIS），（1）推断冰架机械特性的空间和时间变化，（2）从信号传播特性推断整体弹性特性，以及（3）确定RIS对远离锋面观测到的亚重力波强迫的响应是作为来自锋面的应力波传播，还是由穿透RIS空腔的IG波能量“局部”产生。这项工作的知识价值在于，海洋重力波是全球海洋环境的动态要素，受到海洋变暖以及海洋和大气环流模式变化的影响。因此，它们的演变可能通过机械相互作用和潜在的增加基底融化来驱动冰架稳定性的变化，这反过来又会反馈海平面上升。重力波引起的信号在冰架上的传播取决于冰架和冰架下水腔的几何形状（例如结构、厚度、裂缝密度和方向）以及冰架的物理特性。重点将放在观察和模拟的RIS响应IG波强迫周期从75到300秒。由于IG波不会受到海冰的明显阻尼，因此季节性监测将深入了解全年RIS对这种海洋强迫的响应。该项目为期三年，将在区域信息系统上持续收集数据，为期24个月，跨越两个年度周期。RIS冰阵覆盖范围与罗斯海地幔结构（RSMS）研究重叠，为IG波定位提供了有益的扩展阵列。冰架部署将包括16个台站，配备宽带地震仪和气压计。RIS前沿附近的三个地震台站将提供参考响应/强迫函数，并测量整个前沿响应的变化。与前方正交的线性地震台阵将由三个台站与三个RSMS台站串联组成。被动地震阵列监测将用于确定海洋波浪引起的信号源沿着RIS前沿的空间和时间分布，并估计冰架结构，高密度阵列用于监测和定位断裂（冰震）活动。更广泛的影响包括提供基线测量，以便在未来几十年内检测冰架变化，这将有助于科学家和决策者应对气候变化和海平面上升的社会环境挑战。跨学科地球科学的博士后学者将参与整个研究过程。圣地亚哥县Cuyamaca社区学院的学生将为该项目开发和管理一个网站，作为地球科学和海洋学课程的教学工具，并为中学生开发一个有关海浪的网站。

Bromirski/1246151This award supports a project intended to discover, through field observations and numerical simulations, how ocean wave-induced vibrations on ice shelves in general, and the Ross Ice Shelf (RIS), in particular, can be used (1) to infer spatial and temporal variability of ice shelf mechanical properties, (2) to infer bulk elastic properties from signal propagation characteristics, and (3) to determine whether the RIS response to infragravity (IG) wave forcing observed distant from the front propagates as stress waves from the front or is "locally" generated by IG wave energy penetrating the RIS cavity. The intellectual merit of the work is that ocean gravity waves are dynamic elements of the global ocean environment, affected by ocean warming and changes in ocean and atmospheric circulation patterns. Their evolution may thus drive changes in ice-shelf stability by both mechanical interactions, and potentially increased basal melting, which in turn feed back on sea level rise. Gravity wave-induced signal propagation across ice shelves depends on ice shelf and sub-shelf water cavity geometry (e.g. structure, thickness, crevasse density and orientation), as well as ice shelf physical properties. Emphasis will be placed on observation and modeling of the RIS response to IG wave forcing at periods from 75 to 300 s. Because IG waves are not appreciably damped by sea ice, seasonal monitoring will give insights into the year-round RIS response to this oceanographic forcing. The 3-year project will involve a 24-month period of continuous data collection spanning two annual cycles on the RIS. RIS ice-front array coverage overlaps with a synergistic Ross Sea Mantle Structure (RSMS) study, giving an expanded array beneficial for IG wave localization. The ice-shelf deployment will consist of sixteen stations equipped with broadband seismometers and barometers. Three seismic stations near the RIS front will provide reference response/forcing functions, and measure the variability of the response across the front. A linear seismic array orthogonal to the front will consist of three stations in-line with three RSMS stations. Passive seismic array monitoring will be used to determine the spatial and temporal distribution of ocean wave-induced signal sources along the front of the RIS and estimate ice shelf structure, with the high-density array used to monitor and localize fracture (icequake) activity. The broader impacts include providing baseline measurements to enable detection of ice-shelf changes over coming decades which will help scientists and policy-makers respond to the socio-environmental challenges of climate change and sea-level rise. A postdoctoral scholar in interdisciplinary Earth science will be involved throughout the course of the research. Students at Cuyamaca Community College, San Diego County, will develop and manage a web site for the project to be used as a teaching tool for earth science and oceanography classes, with development of an associated web site on waves for middle school students.