AN EXPERIMENTAL STUDY OF GLACIER SLIP OVER HARD AND SOFT BEDS

硬床和软床冰川滑移的实验研究

• 批准号: 1023586
• 负责人: Neal Iverson
• 金额: $ 39.04万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1023586&HistoricalAwards=false
• 关键词: EXPERIMENTAL; STUDY; GLACIER; SLIP; OVER

Movement of glaciers and ice sheets affects their stability and attendant sea-level rise as the climate warms. In addition, ice-sheet movement during the Pleistocene left a spectacular imprint on landscapes. Glaciers that move fastest and modify landscapes most severely move primarily by slip over their rock (hard) or sediment (soft) beds. Increasingly sophisticated theories of this slip have been advanced over the last half-century, but these theories are largely untested, owing to the inaccessibility of glacier beds and the spatial and temporal variability of conditions there. The objective of this project is to use a newly constructed laboratory device to study relationships among glacier slip velocity, basal drag (slip resistance) and effective pressure (ice pressure minus water pressure at the bed). The device drags a ring of melting ice (0.9 m outside diameter, 0.2 m wide, 0.15 m thick) across a hard or soft bed. Features of the device include unlimited slip displacement, temperature control to a few hundredths of degree, and continuous observation of ice sliding and flow separation at the bed. One set of experiments will test the theory that as slip velocity increases, steady drag on a rough, hard bed attains a maximum value and then either remains constant or decreases, depending upon the bed geometry. Basal drag, slip velocity, and effective pressure will be individually varied during slip of ice at its melting temperature over stepped and sinusoidal bed surfaces. Numerical modeling of ice flow under the geometric constraints of the experiment will allow theoretical results to be compared directly with experimental data. A second set of experiments will provide relationships among slip velocity, drag, and effective pressure for soft beds. These experiments will also reveal both the extent to which ice invades the pore spaces of soft beds by melting and refreezing and the degree to which soft beds deform to accommodate slip?problems central to evaluating sediment transport by glaciers. Robust quantitative models of glacier slip are needed to forecast the speeds of glaciers and ice sheets. Glaciers have been observed surging, i.e. moving forward at unusually high velocities, and retreating at various rates, apparently in response to changing climate. The experimental studies of this project will examine glacier movement in a a way that can not be determined from field observations. A more complete analysis of the sliding process will allow glacier slip to be treated more accurately and less arbitrarily in computer models of glacier and ice-sheet motion. This will permit better characterizations of environmental change in the near future and of landscape evolution in the distant past.

随着气候的温暖，冰川和冰盖的运动会影响其稳定性和随之而来的海平面上升。此外，在更新世期间的冰盖运动在景观上留下了壮观的烙印。冰川移动最快并修改景观最严重地通过岩石（硬）或沉积物（柔软）床滑动而移动。在过去的半个世纪中，这种滑动的越来越复杂的理论已经提高了，但是由于冰川床的无法访问以及那里的条件的空间和时间变化，这些理论在很大程度上没有测试。该项目的目的是使用新建的实验室装置来研究冰川滑动速度，基础阻力（滑动电阻）和有效压力（冰压减去床上的水压）之间的关系。该设备在硬床或软床上拖动融化冰环（0.9 m外径，0.2 m宽，厚0.15 m）。该设备的特征包括无限的滑移位移，温度控制至几百度，以及对床上冰滑动和流动分离的连续观察。一组实验将测试以下理论：随着滑移速度的增加，在粗糙的硬床上稳定阻力达到最大值，然后取决于床的几何形状，然后保持恒定或减小。基础阻力，滑动速度和有效压力将在冰滑动过程中在其熔融温度下的熔融温度和正弦床表面上单独变化。在实验的几何约束下对冰流的数值建模将允许将理论结果直接与实验数据进行比较。第二组实验将在滑动速度，阻力和软床的有效压力之间提供关系。这些实验还将揭示冰通过熔化和重新冻结侵入软床的孔隙的程度，以及软床变形以适应滑移的程度？评估冰川沉积物传输的核心。需要强大的冰川滑移定量模型，以预测冰川和冰盖的速度。已经观察到冰川涌动，即以异常高的速度向前移动，并以各种速度撤退，显然是为了响应变化的气候。该项目的实验研究将以无法从现场观察结果确定的方式检查冰川运动。 对滑动过程的更完整分析将使冰川滑移在冰川和冰盖运动的计算机模型中更准确和任意处理。这将允许在不久的将来和遥远过去的景观演变中更好地表征环境变化。