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?

格陵兰的出口冰川加速和退缩，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脉的冰川萎缩：所有这些都在过去十年中成为冰川和冰盖的焦点。海平面上升的速度有多快？冰川作为虚拟“水塔”在干旱的夏季提供水资源的消失速度有多快？我们能从目前的趋势推断吗？解释这些问题需要对过程的理解，因为陆地冰的演变缓慢，而且详细的仪器记录很短。如果不了解驱动观察到的变化的物理学，我们就无法知道它是否以及如何继续下去。 拟议的研究解决了冰川和冰盖动力学中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起的作用所激发的。在相对温和的气候中，夏季会发生大范围的表面融化：不仅是高山冰川，还有广阔的格陵兰冰盖。这些融化物并不停留在冰川表面，而是被引导到河床上。它如何影响滑动一旦在那里？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。水不是到处都流的。水路由如何随时间变化是冰川床对地表水输入的响应的核心。 使用在UBC创建的八年数据集，我们将构建一个完全校准的模型，捕捉排水系统演变的所有重要方面。这样一个模型在试图预测冰川爆发、洪水和冰川涌动时面临着最严峻的考验。直到今天，对冰川涌动的完整解释--某些冰川的间歇性加速，通常是数量级的--仍然是冰川动力学中存在时间最长的问题之一。我们将对这些现象进行系统的理论和观测探索，以进一步完善我们的模型。我们将研究的一个关键问题是冰内水储存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激增。 然而，水的生产不仅限于山区冰川和格陵兰岛。在一个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的基础上，我们将开发在更冷的气候中储水和排水的模型，在那里融化经常发生在浅层地下，由一层薄薄的冰屏蔽寒冷的空气温度。我们的目标是最终了解如何有足够的水可以池，以鼓励水力压裂发生作为一个前兆的产犊。我们要解决的最后一个问题是冰解机制本身：在大多数极地冰盖中主导质量损失的过程是如何工作的，以及如何模拟它？