Collaborative Research: Tidal Modulation of Ice-Stream Flow

该奖项支持一个项目，该项目旨在调查新发现的两个南极西部主要冰流对潮汐振荡的惊人敏感性，以了解这种影响的程度和特征及其对未来冰流行为的影响。冰流D、C和惠兰(B)都显示出强烈但明显的潮汐信号。惠兰的冰原通常被完全阻止，前进运动每天被限制在两个短暂的时间段，涨潮和退潮时。运动事件以地震波的速度传播穿过冰原。在D口附近，潮汐引起冰流速度的正负50%的日变化，这比在惠兰冰川上传播的速度慢，地震数据表明C经历了更慢的潮汐信号在冰川上的传播。观测到C上冰川超过100公里，D上冰川超过40公里的潮汐影响，并可能是惠兰斯上游400公里报告的基本水压波动的原因，惠兰斯几乎是整个冰流的长度。在第一年，这一行为的空间范围将通过五个协调的地震和全球定位系统仪器包在每个冰流上100公里间隔的惠兰冰流和冰流D上进行测量。这些装置将由Twin Otter通过审查卫星图像而选定的地点部署，并将通过太阳能和电池的组合在两个月球周期内自主运行，以研究冰流运动对大潮和小潮的敏感性。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相反的行为。第二和第三个野外季节将更详细地研究惠兰(第二年)和D(第三年)的潮汐行为。工作将特别侧重于详细研究惠兰事件的至少一个震源区，假设从初步数据推断的震源区仍然活跃。垂直运动尚未被探测到，但差分GPS将提高我们的探测灵敏度。地震仪器将极大地提高时间分辨率和测量传播速度和任何空间非均质性的能力。随着从现场实验中了解到更多知识，建模将得到改进。该项目应该产生许多更广泛的影响。这项研究增进了对冰流行为的了解，这将有助于评估影响全球海平面并产生社会后果的冰盖快速变化的可能性。结果将通过科学出版物和专业会议上的演讲以及与媒体的接触、由私人助理教授的大学课程、对学校和社区团体的访问以及其他活动来传播。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.