Collaborative Research: Outbursts from an Ice-Dammed Lake

合作研究：冰堰湖的爆发

• 批准号: 9812944
• 负责人: Joseph Walder
• 金额: $ 1.57万
• 依托单位: Geological Survey-Menlo Park
• 依托单位国家: 美国
• 项目类别: Interagency Agreement
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-02-15 至 2000-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9812944&HistoricalAwards=false
• 关键词: Collaborative; Research; Outbursts; Ice; Dammed

This is a collaborative study which includes Portland State University, the U.S. Geological Survey, and University of California, Santa Cruz. Outburst floods, or jokulhlaups, occur when ice-dammed water bodies drain suddenly. These floods can have devastating downstream effects. They can dramatically reshape stream channels and can be a hazard to human settlements. The mechanisms (timing, size, and geomorphic effect of outburst floods) by which impounded water is stored and released have been poorly studied because outburst floods are unpredictable. What is known comes primarily from observations in Iceland where subglacial and ice marginal lakes drain periodically. Elsewhere, observations have been serendipitous or after the fact. The Principal Investigators will investigate a site with predictable, annual outbursts on the Kennicott Glacier in Wrangell-St. Elias National Park, Alaska. The drainage of ice-marginal Hidden Creek Lake endangers nearby residents and visitors to the National Park.The Principal Investigators will examine outburst flood triggering to begin testing and refining existing theoretical models. Their hypothesis is that the ice dam does not form a "tight" hydraulic seal that is abruptly broken by flotation. Instead, as the lake level rises, it initially becomes connected to a distributed basal drainage system resulting in a slow, stable leak. The lake level eventually rises enough that hydraulic connection is established with an arborescent channel network away from the edge of the glacier. The lake then drains rapidly, and may be related to seasonal development of a conduit system or to the termination state of a glacier surge.There are four main components to the field work: 1) to measure ice-dam deformation as the lake fills and empties and characterize how the ice dam behaves mechanically; 2) to measure lake level as a function of time, determine lake hypsometry, and measure the lake's thermal structure. These data will constitute fundamental boundary conditions to constrain models of the outburst floods; 3) to examine the hydraulic integrity of the ice dam and temporal changes in the subglacial drainage system using boreholes; and 4) to monitor the flood and changes in channel morphology in the outlet river near the glacier terminus. They will use ground penetrating radar to survey the stream bed which will rapidly give detailed cross sections and will be used to calibrate discharge and to document channel changes during the flood. This study should provide a better understanding of outburst floods and improve prediction methods. The results will provide insight into glaciological processes such as seasonal drainage system evolution, surge termination, and the link between basal hydrology and glacier dynamics.

这是一项合作研究，包括波特兰州立大学、美国地质调查局和圣克鲁斯的加州大学。 当冰坝的水体突然流失时，就会发生爆发性洪水。这些洪水可能对下游造成破坏性影响。 它们可以极大地改变河道，并可能对人类住区造成危害。 由于突发洪水是不可预测的，因此对蓄水储存和释放的机制（突发洪水的时间、规模和地貌效应）的研究很少。 我们所知道的主要来自冰岛的观测，那里的冰下湖和冰缘湖定期排水。 在其他地方，观察是偶然的或事后的。 主要调查人员将调查阿拉斯加兰格尔-圣埃利亚斯国家公园肯尼科特冰川上一个可预测的年度喷发地点。 冰缘隐溪湖的排水危及附近居民和国家公园的游客。首席调查员将研究突发洪水的触发情况，以开始测试和完善现有的理论模型。 他们的假设是，冰坝并没有形成一个“紧密”的液压密封，这是突然打破漂浮。 相反，随着湖平面的上升，它最初会连接到一个分布式的基底排水系统，导致缓慢，稳定的泄漏。 湖平面最终上升到足以与远离冰川边缘的树木河道网络建立水力连接。 冰坝的形成与冰坝的形成密切相关，冰坝的形成与冰坝的形成和冰坝的融化密切相关，冰坝的形成与冰坝的融化密切相关，冰坝的形成与冰坝的融化密切相关。2）测量湖平面随时间的变化，确定湖的高度，并测量湖的热结构。这些数据将构成基本的边界条件，以约束模型的突发洪水; 3）检查冰坝的水力完整性和时间变化的冰下排水系统使用钻孔;和4）监测洪水和变化的渠道形态在出口河流冰川终点附近。 他们将使用地面穿透雷达来测量河床，这将迅速提供详细的横截面，并将用于校准流量和记录洪水期间的河道变化。 这项研究将有助于更好地了解突发洪水并改进预测方法。 结果将提供深入了解冰川过程，如季节性排水系统的演变，浪涌终止，以及基础水文和冰川动力学之间的联系。