Hydraulic and mechanical controls on fast glacier flow

对快速冰川流动的液压和机械控制

• 批准号: RGPIN-2018-04665
• 负责人: Schoof, Christian
• 金额: $ 5.08万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712560
• 关键词: Hydraulic; mechanical; controls; fast; glacier

Accelerating and retreating outlet glaciers in Greenland, large icebergs calving off Antarctica, shrinking glaciers in the Alps, the Rockies and the Himalayas: all these have been shining a spotlight on glaciers and ice sheets over the last decade. How fast will sea levels rise? How fast will glaciers disappear as virtual "water towers", providing water resources during dry summers? Can we extrapolate from current trends? Answering these questions requires process understanding, because land ice evolves slowly and the detailed instrumental record is short. Without understanding the physics driving observed change, we cannot know if and how it will continue. The proposed research tackles four interlinked questions in glacier and ice sheet dynamics, all motivated by the role melt water plays in changing ice flow. In relatively temperate climates, surface melt occurs widely in summer: not only on mountain glaciers, but also the vast Greenland ice sheet. That melt does not stay at the glacier surface, but is routed to the bed. How does it affect sliding once there? This is the first question we tackle. The configuration of the drainage system under the ice is the key to sliding: if it sustains high water pressure, faster ice motion occurs. However, recent observations by my group and others underline the importance of a patchy drainage system. Water does not flow everywhere. How water routing changes over time is central to the response of the glacier bed to surface water input. Using an eight-year data set created at UBC, we will construct a fully calibrated model that captures all essential aspects of drainage system evolution. Such a model faces its sternest test in trying to predict glacier outburst floods and glacier surges. To this day, a full explanation of glacier surges - episodic accelerations of certain glaciers, often by orders of magnitude - remains one of the longest-standing problems in glacier dynamics. We will undertake a systematic theoretical and observational exploration of these phenomena in order to refine our models further. A key question we will study is how englacial water storage interacts with the drainage system, and whether feedbacks between the two can cause glacier surges. Water production is however not limited to mountain glaciers and Greenland. Building on a three-year field project studying surface melt features on an Antarctic outlet glacier and their relationship with ice dynamics, we will develop models for water storage and drainage in much colder climates, where melting often occurs in the shallow subsurface, shielded from frigid air temperatures by a thin layer of ice. Our goal is ultimately to understand how enough water can pool to encourage hydrofracturing to occur as a precursor to calving. The last question we tackle is that of calving mechanisms themselves: how does the process that dominates mass loss in most polar ice caps work, and how can it be modelled?

格陵兰岛冰川的加速和后退，南极洲的大型冰山崩解，阿尔卑斯山、落基山脉和喜马拉雅山的冰川萎缩：所有这些在过去十年中都成为人们关注冰川和冰盖的焦点。海平面上升的速度有多快？冰川会以多快的速度消失，成为虚拟的“水塔”，在干燥的夏季提供水资源？我们可以从当前趋势推断吗？回答这些问题需要了解过程，因为陆地冰演化缓慢，详细的仪器记录也很短。如果不了解驱动观察到的变化的物理原理，我们就无法知道它是否会持续以及如何持续。 拟议的研究解决了冰川和冰盖动力学中的四个相互关联的问题，所有这些问题都是由融水在改变冰流中所扮演的角色引起的。在相对温和的气候下，夏季广泛发生地表融化：不仅在山地冰川上，而且在广阔的格陵兰冰盖上也如此。融化的水不会停留在冰川表面，而是被输送到河床上。一旦到达那里，它如何影响滑动？这是我们要解决的第一个问题。冰下排水系统的配置是滑动的关键：如果它能承受高水压，冰的运动就会更快。然而，我的团队和其他人最近的观察强调了不完整的排水系统的重要性。水并非到处流动。水流路径如何随时间变化是冰川床对地表水输入的响应的核心。 使用 UBC 创建的八年数据集，我们将构建一个完全校准的模型，捕获排水系统演变的所有基本方面。在试图预测冰川溃决洪水和冰川涌动时，这样的模型面临着最严峻的考验。迄今为止，对冰川涌动（某些冰川的间歇性加速，通常达到几个数量级）的完整解释仍然是冰川动力学中最长期存在的问题之一。我们将对这些现象进行系统的理论和观察探索，以进一步完善我们的模型。我们要研究的一个关键问题是冰川储水如何与排水系统相互作用，以及两者之间的反馈是否会导致冰川涌动。 然而，水的生产并不限于山区冰川和格陵兰岛。基于一项为期三年的实地项目，研究南极出口冰川的表面融化特征及其与冰动力学的关系，我们将开发在寒冷气候下的储水和排水模型，在这些气候中，融化通常发生在不受寒冷影响的浅层地下。空气温度受到一层薄冰的影响。我们的最终目标是了解如何聚集足够的水来促进水力压裂的发生，作为崩解的前兆。我们解决的最后一个问题是崩解机制本身：在大多数极地冰盖中主导质量损失的过程是如何运作的，以及如何对其进行建模？