The role of atmospheric forcing on the dynamic stability of Greenland's outlet glaciers

大气强迫对格陵兰岛出口冰川动态稳定性的作用

• 批准号: NE/F021399/1
• 负责人: Peter Nienow
• 金额: $ 28.32万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF021399%2F1
• 关键词: role; atmospheric; forcing; dynamic; stability

This project will quantify the effect of surface generated melt-water fluctuations on ice motion at the margin of the Greenland Ice Sheet (GrIS). More specifically, it will provide data that will enable ice-sheet modellers to improve their predictions of the future contribution of the GrIS to sea level rise in response to a warming world. To achieve this aim requires a dedicated field campaign to the GrIS to investigate seasonal ice flow dynamics and runoff processes along flow parallel transects extending from the ice sheet margin to the equilibrium line altitude (ELA) at both tidewater and land-terminating glaciers. The greatest store of fresh water in the northern hemisphere - equivalent to 7m of eustatic sea level rise - is held within the Greenland Ice Sheet (GrIS), and yet its present and future contribution to sea level is poorly constrained (IPCC, 2007). Recent observations suggest that mass loss near the margin of the GrIS is accelerating through a combination of increased surface melting (e.g. Steffen et al, 2004) and dynamic thinning (e.g. Rignot and Kanagaratnam, 2006). However, the key processes controlling dynamic thinning have yet to be identified (Alley et al, 2005), and in consequence, are not incorporated in the ice-sheet models which form the basis of the IPCC sea level projections. This in part reflects the fact that the satellite data that has revealed the widespread speed-up of glaciers cannot be acquired at the temporal resolution needed to resolve the causal mechanisms. Our present understanding of GrIS mass balance is especially complicated by uncertainties in the sensitivity of ice-marginal dynamics to changes in melt-water induced lubrication resulting from penetration of supraglacial melt-waters to the glacier bed (Zwally et al, 2002). Recent observations on the GrIS Shepherd et al, in review) reveal, over a five day period in July, a strong and direct coupling between surface hydrology and dynamics where diurnal fluctuations in velocity of >100% occur and where maximum daily velocities scale with temperature. Such observations confirm the need to acquire hydrological and dynamic data at high temporal (sub-hourly) and spatial resolution throughout the year to parameterise the coupling between ice melting and flow. This project will collect data at the necessary resolution to quantify the relationship between melt-water production and ice sheet dynamics thereby enabling ice-sheet modellers to improve predictions of the GrIS's response to climate change. We will conduct ground based experiments along two flow-parallel transects at the western margin of the GrIS in adjacent land and marine terminating drainage basins to address the following objectives: 1. Is there a temporal and spatial pattern to any hydrology-dynamic link associated with the seasonal evolution of the supraglacial drainage system (including supraglacial lakes)? 2. Over what area does surface generated meltwater penetrate to the base of the ice sheet? 3. Is there a relationship between the volume of meltwater input at the glacier surface and the magnitude of the dynamic response? 4. Do tidewater and land-terminating glaciers behave differently during the course of a melt-season? Field campaigns will be undertaken during 2008 and 2009 to determine: 1) The rate, extent and duration of melt. 2) The temporal and spatial variations in water volumes stored in and released from supraglacial lakes and delivered to freely draining moulins. 3) The seasonal, diurnal and hourly variations in ice dynamics. 4) The variations in proglacial discharge and water chemistry (at Russell Glacier). As a result of our work, it will be possible to determine whether ice dynamics at the margin of the GrIS is significantly affected by lubrication of the glacier bed following the drainage of surface derived meltwaters. Our results will be delivered to ice sheet modellers to help them constrain predictions for the future of the GrIS

该项目将量化地表产生的融水波动对格陵兰冰盖（GrIS）边缘冰运动的影响。更具体地说，它将提供数据，使冰盖建模者能够改进对 GrIS 对海平面上升的未来贡献的预测，以应对全球变暖。为了实现这一目标，需要对 GrIS 进行专门的实地调查，以研究潮水冰川和陆地终端冰川沿从冰盖边缘延伸到平衡线高度 (ELA) 的流动平行横断面的季节性冰流动力学和径流过程。北半球最大的淡水储备——相当于海平面上升 7m——位于格陵兰冰盖 (GrIS) 内，但其当前和未来对海平面的贡献却很少受到限制（IPCC，2007）。最近的观察表明，通过增加表面熔化（例如 Steffen 等人，2004 年）和动态减薄（例如 Rignot 和 Kanagaratnam，2006 年）的结合，GrIS 边缘附近的质量损失正在加速。然而，控制动态减薄的关键过程尚未确定（Alley 等人，2005 年），因此并未纳入构成 IPCC 海平面预测基础的冰盖模型中。这在一定程度上反映了这样一个事实：揭示冰川普遍加速的卫星数据无法以解决因果机制所需的时间分辨率获得。我们目前对 GrIS 质量平衡的理解尤其复杂，因为冰缘动力学对由于冰上融水渗透到冰川床而引起的融水引起的润滑变化的敏感性的不确定性（Zwally 等，2002）。最近对 GrIS Shepherd 等人的观察（综述中）揭示，在 7 月的五天内，地表水文学和动力学之间存在强烈且直接的耦合，其中速度的日波动发生 >100%，并且最大日速度随温度变化。这些观测证实需要全年获取高时间（亚小时）和空间分辨率的水文和动态数据，以参数化冰融化和流动之间的耦合。该项目将以必要的分辨率收集数据，以量化融水产生和冰盖动态之间的关系，从而使冰盖建模者能够改进 GrIS 对气候变化响应的预测。我们将沿着 GrIS 西缘邻近陆地和海洋终止流域的两条平行流横断面进行地面实验，以实现以下目标： 1. 与冰上排水系统（包括冰上湖泊）季节演变相关的任何水文动力联系是否存在时间和空间模式？ 2. 地表产生的融水在什么区域渗透到冰盖底部？ 3、冰川表面融水输入量与动态响应大小之间是否存在关系？ 4. 在融化季节期间，潮水冰川和陆地终止冰川的行为是否有所不同？ 2008 年和 2009 年期间将开展实地活动，以确定： 1) 融化的速度、范围和持续时间。 2）冰上湖泊储存和释放的水量的时间和空间变化，并输送到自由排水的冰臼。 3）冰动态的季节、昼夜和小时变化。 4) 冰川前流量和水化学的变化（拉塞尔冰川）。我们的工作结果将有可能确定 GrIS 边缘的冰动力学是否受到地表融水排出后冰川床润滑的显着影响。我们的结果将提供给冰盖建模者，帮助他们限制对 GrIS 未来的预测

项目成果

Rapid erosion beneath the Greenland ice sheet

• DOI: 10.1130/g32687.1
• 发表时间: 2012-04-01
• 期刊: GEOLOGY
• 影响因子: 5.8
• 作者: Cowton, T.;Nienow, P.;Mair, D.
• 通讯作者: Mair, D.

Variability in ice motion at a land-terminating Greenlandic outlet glacier: the role of channelized and distributed drainage systems

• DOI: 10.1017/jog.2016.36
• 发表时间: 2016-06
• 期刊: Journal of Glaciology
• 影响因子: 3.4
• 作者: T. Cowton;P. Nienow;A. Sole;I. Bartholomew;D. Mair

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

• DOI: 10.5194/tc-9-123-2015
• 发表时间: 2015-01-01
• 期刊: CRYOSPHERE
• 影响因子: 5.2
• 作者: Clason, C. C.;Mair, D. W. F.;Schwanghart, W.
• 通讯作者: Schwanghart, W.

E-tracers: Development of a low cost wireless technique for exploring sub-surface hydrological systems

电子示踪剂：开发用于探索地下水文系统的低成本无线技术

• DOI: 10.1002/hyp.9451
• 发表时间: 2012
• 期刊: Hydrological Processes
• 影响因子: 3.2
• 作者: Bagshaw E