Seismic characterisation of subglacial conditions beneath the margin of the West Greenland Ice Sheet

西格陵兰冰盖边缘冰下条件的地震特征

• 批准号: NE/H012869/1
• 负责人: Bernd Kulessa
• 金额: $ 5.31万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH012869%2F1
• 关键词: Seismic; characterisation; subglacial; conditions; beneath

The response of the Greenland Ice Sheet to a warming climate is of great significance for models of sea-level rise. As such, it receives significant attention from the media, among the general public and in government policy decisions. However, its behaviour is influenced by a number of complex processes, the interactions between which are not well understood. The ice sheet is therefore a focus of major scientific research campaigns, exploring the key influences on its stability and how it will evolve in the future. Recent research has suggested that water is a significant influence on ice sheet stability. Water that is present at the base of the ice sheet acts as a lubricant between the ice and the material beneath it, allowing the ice to move at a faster velocity. For the West Greenland Ice Sheet, a source of basal water is stored in surface meltwater lakes. These form at the start of the summer melt season, in June and July, and typically undergo one or more drainage events throughout July and August. It is believed that the water they contain drains through a network of cracks in the ice, eventually reaching the base of the ice sheet and causing a dynamic response. The drainage of these lakes is rather sudden (in one example, a lake with an area around 6 km2 was drained in under 2 hours) hence a large volume of water can be introduced to the bed of the ice sheet in a short space of time. Certain scientific groups have observed the drainage of a meltwater lake, and have detected increases in local ice dynamics very soon after; this clearly implies that the theory of meltwater reaching the bed of the ice sheet is correct. However, the delivery of meltwater has never been imaged directly; it has only been inferred from responses in other datasets. In this proposal, we intend to detect, delineate and quantify the passage of meltwater at the bed of the ice sheet in seismic geophysical data, which are widely used for this purpose in other areas of the earth sciences and commercial practice. The geophysical techniques we propose have been extensively applied to estimating the fluid content in the subsurface. Water modifies the physical properties of the subsurface to which seismic energy is particularly sensitive. We therefore intend to use geophysics to continually monitor the base of the ice sheet, throughout the melt-and-drainage season in July and August. We anticipate that our seismic data would show the basal water content to increase gradually, as an increasing number of meltwater lakes drain in the vicinity of the survey site. Our specific field site is located amongst a cluster of lakes and moulins (vertical or sub-vertical openings facilitating water drainage into the ice body), and located directly over an area of the ice sheet previously shown to respond to lake drainage events. We are therefore confident that if that response is due to the delivery of meltwater to the bed of the ice sheet, that meltwater will be detectable by our geophysical survey. Our observations will be complemented by a range of results from complementary scientific projects already underway at the site. This includes, e.g., airborne and ground-based radar, passive seismic and GPS assessment or monitoring, and a new catchment-scale model of surface-melt coupled dynamic feedbacks. Meltwater is an important influence on ice dynamics that, with continued global warming, is likely to become more significant in the future. Understanding that influence is therefore crucial for predicting how the Greenland Ice Sheet will respond to climate change, and the observations made during this study will undoubtedly contribute to our knowledge of ice dynamics.

格陵兰冰盖对气候变暖的响应对于海平面上升模型具有重要意义。因此，它受到媒体、公众和政府决策的极大关注。然而，它的行为受到许多复杂过程的影响，这些过程之间的相互作用还没有被很好地理解。因此，冰盖是重大科学研究活动的焦点，探索对其稳定性的关键影响以及未来它将如何演变。最近的研究表明，水对冰盖的稳定性有重大影响。冰盖底部的水在冰和冰下的物质之间起到了润滑剂的作用，使冰以更快的速度移动。对于西格陵兰冰盖，基础水的来源储存在表面融化的湖泊中。它们在夏季融化季节开始时形成，在6月和7月，通常在整个7月和8月经历一次或多次排水事件。据信，它们所含的水通过冰层上的裂隙网络排出，最终到达冰盖底部，并引起动态反应。这些湖泊的排水是相当突然的(在一个例子中，一个面积约6平方公里的湖泊在不到2小时内就被排干了)，因此可以在短时间内将大量水引入冰盖的底部。某些科学小组观察到了融水湖的排水，并很快检测到当地冰川动态的增加；这显然意味着融水到达冰盖底部的理论是正确的。然而，融化水的输送从未被直接成像；它只是从其他数据集中的反应中推断出来的。在这项提议中，我们打算在地震地球物理数据中探测、描绘和量化冰盖底部的融水通道，这些数据在地球科学的其他领域和商业实践中被广泛用于此目的。我们提出的地球物理技术已被广泛应用于地下流体含量的估计。水改变了地下的物理性质，地震能量对此特别敏感。因此，在7月和8月的融化和排水季节，我们打算使用地球物理学来持续监测冰盖的底部。我们预计我们的地震数据将显示，随着越来越多的融水湖泊在调查地点附近排出，基础水含量将逐渐增加。我们的特定现场地点位于湖泊和冰山(垂直或次垂直开口，便于将水排放到冰体中)集群之间，并且直接位于先前显示的响应湖泊排水事件的冰盖区域。因此，我们相信，如果这种反应是由于融化的水输送到冰盖的床上，那么我们的地球物理调查将可以探测到融化的水。我们的观察将得到现场已在进行的补充性科学项目的一系列结果的补充。这包括例如机载和陆基雷达、被动地震和全球定位系统评估或监测，以及新的地表-熔融耦合动态反馈的集水尺度模型。融水对冰川动力学有重要影响，随着全球持续变暖，这种影响在未来可能会变得更加重要。因此，了解这种影响对于预测格陵兰冰盖将如何应对气候变化至关重要，而在这项研究期间所做的观察无疑将有助于我们对冰动力学的了解。

项目成果

Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

• DOI: 10.5194/tc-7-129-2013
• 发表时间: 2013-01-01
• 期刊: CRYOSPHERE
• 影响因子: 5.2
• 作者: Doyle, S. H.;Hubbard, A. L.;Box, J. E.
• 通讯作者: Box, J. E.

Modeling of subglacial hydrological development following rapid supraglacial lake drainage.

• DOI: 10.1002/2014jf003333
• 发表时间: 2015-06
• 期刊: Journal of geophysical research. Earth surface
• 作者: Dow CF;Kulessa B;Rutt IC;Tsai VC;Pimentel S;Doyle SH;van As D;Lindbäck K;Pettersson R;Jones GA;Hubbard A
• 通讯作者: Hubbard A

An automated approach to the location of icequakes using seismic waveform amplitudes

使用地震波形振幅自动定位冰震的方法

• DOI: 10.3189/2013aog64a074
• 发表时间: 2017
• 期刊: Annals of Glaciology
• 影响因子: 2.9
• 作者: Jones G

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

• DOI: 10.1144/sp461.8
• 发表时间: 2017-05
• 期刊: Special Publications
• 作者: M. Siegert;B. Kulessa;M. Bougamont;P. Christoffersen;K. Key;Kristoffer R. Andersen;A. Booth;A. Smith

Advancements in the measurement of the cryosphere using geophysics - Introduction

利用地球物理学测量冰冻圈的进展 - 简介

• DOI: 10.1190/2015-1120-spseintro.1
• 发表时间: 2016
• 期刊: GEOPHYSICS
• 影响因子: 3.3
• 作者: Parsekian A