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

Bromirski/1246151本奖项支持一个项目，该项目旨在通过现场观测和数值模拟，发现海浪对一般冰架，特别是罗斯冰架(RIS)的振动如何可用于(1)推断冰架力学性质的时空变异性，(2)根据信号传播特征推断整体弹性性质，以及(3)确定RIS对远离锋面观测到的亚重力(IG)波强迫的响应是作为应力波从锋面传播，还是由穿透RIS空腔的IG波能量“局部”产生。这项工作的学术价值在于，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，它们的演化可能会通过机械相互作用和潜在的增加基础融化来推动冰架稳定性的变化，这反过来又会反馈到海平面上升。重力波在冰架上的传播取决于冰架和次冰架水腔的几何形状(如结构、厚度、裂缝密度和方位)，以及冰架的物理性质。重点是观测和模拟S 75-300时IG波强迫的RIS响应。由于IG波不受海冰的明显抑制，季节性监测将使RIS对这种海洋强迫的全年响应有更深入的了解。这个为期3年的项目将涉及24个月的持续数据收集，时间跨度为RIS的两个年度周期。RIS冰锋阵列覆盖范围与罗斯海地幔结构(RSMS)协同研究重叠，提供了有利于IG波定位的扩展阵列。冰架部署将由配备宽带地震仪和气压计的16个站组成。RIS锋面附近的三个地震台将提供参考响应/强迫函数，并测量整个锋面响应的可变性。与前线垂直的线性地震台阵将由三个台站和三个RSMS台站组成。被动地震台阵监测将用于确定海浪诱发信号源沿RIS前缘的时空分布，并估计冰架结构，高密度台阵将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，以便能够检测未来几十年的冰架变化，这将有助于科学家和政策制定者应对气候变化和海平面上升的社会环境挑战。一名跨学科地球科学的博士后学者将参与整个研究过程。圣地亚哥县库亚马卡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相关的WAVE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.