Collaborative Research: Linking Subglacial Hydrology and Sliding Dynamics Through Variations Along the Glacial Length

摘要：基底滑动是大多数温带冰川的主要运动形式，它导致冰川涌流，导致冰川侵蚀河床，并经常控制冰川的整体质量分布。冰川的变形速度场可以在一定程度上进行模拟，但目前还没有能够准确预测冰川滑动运动的有效模型。事实上，可能进入滑动模型的变量还没有完全建立起来。从理论上讲，升高的水压和床层蓄水共同促进了滑动。然而，之前的油田项目将滑动速率与压力或储存量相关联，其中大多数与压力有关。这些观测项目仅使用有限的空间和时间分布的测量值来关联滑动和冰下条件。这使得这项任务变得非常困难，因为冰下排水系统是短暂的，而内部冰动力学（例如纵向耦合）使冰川对其下边界变化的响应复杂化。首席研究员将进行多方面的研究，重点关注冰下水文和冰动力系统之间耦合的时间/空间变异性，他们认为这是对滑动动力学新理解的关键。他们将在阿拉斯加东南部温带山谷冰川Bench冰川上进行实地考察。将使用各种类型的仪器收集综合数据集，包括基础水压、地表运动、内部变形、滑动速度、河床的视频观测，以及冰下水流的段塞、泵和示踪剂实验。这些数据将包括至少三个先前未涉及的要素，从而能够对冰下水文与冰川运动之间的联系进行新的探索：1)数据将在两个长度尺度上收集，包括跨越整个冰川的测量和专注于一小段区域的详细测量；2)测量将在至少一年的时间周期内进行，允许对短周期和长周期进行调查；3)自动测量仪器将允许对冰川运动进行不间断的高时间分辨率研究。在第一个实地考察季节，他们将把重点放在长尺度（公里）上，在横跨冰川长度的各个地点测量基础条件和速度。数据将用于研究床和冰动力学之间的纵向耦合。在第二个实地季节，他们将处理较短的长度尺度（10-100米），使当地观测能够置于区域过程的背景下。这样就可以将地表隆起的测量结果与冰动力学和水文学进行全面比较，以研究隆起的原因。所产生的数据集和分析将用于检验和改进冰下水流的概念和数值模型，并建立水文学和冰动力学之间的联系。

ABSTRACTHarperOPP-0118488PfefferOPP-0118721Basal sliding is the principle form of movement of most temperate glaciers and leads to glacier surging, causes glaciers to erode their beds, and often controls the overall glacier's mass distribution. A glacier's deformational velocity field can be modeled with some confidence, but there are no working models that will accurately predict the sliding motion of glaciers. In fact, the variables that would potentially go into a sliding model have not been fully established. Theoretically, sliding is promoted by both elevated water pressure and water storage at the bed. Previous field programs, however, have correlated sliding rate with either pressure or storage, with the majority of associations made with pressure. These observational programs have correlated sliding and subglacial conditions by using only limited spatially and temporally distributed measurements. This has made the task very difficult because the subglacial drainage system is transient and internal ice dynamics (e.g., longitudinal coupling) complicate the glacier's response to change at its lower boundary. The Principal Investigators will conduct a multifaceted study focusing on time/space variability in coupling between the subglacial hydrology and ice dynamics system which they believe is key to a new understanding of sliding dynamics. They will conduct a field campaign on the Bench Glacier, a temperate valley glacier in southeast Alaska. Various types of instrumentation will be used to collect a comprehensive data set of measurements of basal water pressure, surface motion, internal deformation, sliding velocity, video observations of the bed, and slug, pump, and tracer experiments on subglacial water flow. These data will include at least three elements which have not been previously addressed, thus enabling new explorations of the linkages between subglacial hydrology and glacier motion: 1) data will be collected at two length scales, including measurements spanning the entire glacier and detailed measurements focused on a small reach; 2) measurements will be made over a time period of at least a year, allowing short to long period cycles to be investigated; and 3) an automated survey instrument will allow for uninterrupted high-time resolution studies of glacier motion. During the first field season, they will focus on the long length scale (kilometers), with measurements of basal conditions and velocity made at locations spanning the length of the glacier. Data will be used to investigate the longitudinal coupling between the bed and ice dynamics. During the second field season, they will address a short length scale (10-100 meters), enabling local observations to be placed within the context of regional processes. This will permit measurements of surface uplift to be fully compared with both ice dynamics and hydrology to investigate the cause of the uplift. The resulting data set and analyses will be used to test and refine conceptual and numerical models for subglacial water flow and to establish links between hydrology and ice dynamics.