Collaborative Research: Tidal Modulation of Ice-Stream Flow

该奖项支持一个项目，以调查新发现的，令人惊讶的两个主要的西南极冰流潮汐振荡的敏感性，以了解影响的程度和性质及其对未来冰流行为的影响。冰流D、C和Whillans（B）都显示出强烈但明显的潮汐信号。惠兰的冰原通常完全停止，每天的前进运动仅限于两个短暂的时期，在涨潮和落潮时。运动事件以地震波的速度在冰原上传播。在D口附近，潮汐导致冰流速度的昼夜正负50%的变化，冰流速度的上升速度比Whillans更慢，地震数据显示，C经历了更慢的潮汐信号的上升速度。潮汐的影响，观察到超过100公里的upglacier的C，超过40公里upglacier的D，并可能负责基础水压力的波动报告上游400公里的Whillans，几乎整个长度的冰流。 在第一年期间，将在惠兰冰流和冰流D上测量这种行为的空间范围，在每个冰流上以100公里的间隔放置五个协调的地震和全球定位系统仪器包。这些组件将由Twin Otter部署在通过审查卫星图像选定的地点，并将在两个月球周期内通过太阳能和电池动力的组合自动运行，以研究冰流运动对春季和小潮的敏感性。此外，将进一步检查现有的数据集，以寻找有关机制的线索，并将开发初步模型，以协调在冰流上观察到的看似截然不同的行为。 第二和第三场季将更详细地研究Whillans（第2年）和D（第3年）的潮汐行为。工作将特别侧重于详细研究Whillans事件的至少一个源区，假设从初步数据推断的源区仍然活跃。垂直运动尚未被探测到，但差分GPS将增加我们的探测灵敏度。地震仪器将大大提高时间分辨率和测量传播速度和任何空间异质性的能力。随着从实地实验中了解到更多的情况，将对建模进行改进。该项目将产生许多更广泛的影响。这项研究对冰流行为的进一步了解将有助于评估冰盖快速变化影响全球海平面的可能性和社会后果。将通过科学出版物和专业会议上的演讲，以及与新闻界的联系，PI教授的大学课程，访问学校和社区团体以及其他活动来传播结果。两名研究生将通过该项目接受教育。

This award supports a project to investigate the new-found, startling sensitivity of two major West Antarctic ice streams to tidal oscillations to learn the extent and character of the effect and its ramifications for future ice-stream behavior. Ice streams D, C and Whillans (B) all show strong but distinct tidal signals. The ice plain of Whillans is usually stopped outright, forward motion being limited to two brief periods each day, at high tide and on the falling tide. Motion events propagate across the ice plain at seismic wave velocities. Near the mouth of D, tides cause a diurnal plus or minus 50% variation in ice-stream speed that propagates upglacier more slowly than on Whillans, and seismic data show that C experiences even slower upglacier propagation of tidal signals. Tidal influences are observed more than 100 km upglacier on C, more than 40 km upglacier on D, and may be responsible for fluctuations in basal water pressure reported 400 km upstream on Whillans, nearly the full length of the ice stream. During the first year, the spatial extent of this behavior will be measured on Whillans Ice Stream and ice stream D by five coordinated seismic and GPS instrument packages at 100-km spacing on each ice stream. These packages will be deployed by Twin Otter at sites selected by review of satellite imagery and will operate autonomously through a combination of solar and battery power for two lunar cycles to study the sensitivity of the ice stream motion to spring and neap tides. Additionally, existing data sets will be examined further for clues to the mechanisms involved, and preliminary models will be developed to reconcile the seemingly contrasting behaviors observed on the ice streams. The second and third field seasons will examine in greater detail the tidal behavior of Whillans (year 2) and D (year 3). Work will especially focus on detailed study of at least one source area for events on Whillans, assuming that source areas inferred from preliminary data remain active. Vertical motions have not yet been detected, but differential GPS will increase our detection sensitivity. Seismic instrumentation will greatly increase temporal resolution and the ability to measure the propagation speed and any spatial heterogeneity. Modeling will be refined as more is learned from the field experiments. The project should yield numerous broader impacts. The improved knowledge of ice-stream behavior from this study will contribute to assessment of the potential for rapid ice-sheet change affecting global sea level with societal consequences. Results will be disseminated through scientific publication and talks at professional meetings, as well as contacts with the press, university classes taught by the PIs, visits to schools and community groups, and other activities. Two graduate students will be educated through the project.