The influence of evolving bed topography on marine ice stream stability.

由于气候变暖导致海平面上升的风险，南极和格陵兰冰盖的未来稳定性非常重要。然而，对冰盖行为的控制尚不完全清楚。有一个潜在的控制因素没有得到应有的重视，那就是不断变化的地层地形的重要性。本研究旨在测试冰盖如何通过冰川侵蚀和沉积过程响应冰下地形的演变模式。观测表明，侵蚀和沉积可以迅速而显著地改变冰下地貌的形状。这些变化可能在几十年到几百年甚至更长的时间尺度上对上覆冰的行为产生影响。例如，地质资料和理论表明，侵蚀可能使冰流不稳定，导致冰盖迅速退缩，而沉积可能使冰流稳定或前进。该项目的方法是建立一个计算机模型，该模型集成了冰流侵蚀和沉积沉积物的能力，以及监测冰流如何反应的能力。尽管侵蚀和沉积对于控制冰盖对气候或海平面变化的敏感性具有潜在的重要性，但以前从未开发过这样的模型。因此，该项目针对未来冰盖行为的一个潜在关键问题。这是由于收集了大量的数据，这些数据有助于量化侵蚀和沉积发生的速度和模式。这些数据由来自世界各地的合作者提供，可用于控制模型，以便进行真实，稳健和可重复的模拟。这对模型捕捉和预测冰流对不同控制因素的真实敏感性的能力有信心是很重要的。该模型将用于提出3个关键问题：1)在陆地冰和浮冰之间的过渡阶段，沉积物楔块的沉积能否稳定冰流，防止未来海平面上升和气候变暖？2)冰川侵蚀是否会导致冰流退缩，如果是，在什么时间尺度上？3)未来随着海平面上升和气候变暖，西南极洲的惠兰斯冰流将如何应对侵蚀和沉积？惠兰斯冰流在这里被用作一个测试案例，因为它是了解冰流冰下条件的主要努力的焦点。因此，它是现代监测最好的系统之一，其冰流、基底侵蚀和沉积的数据将用于构建当今行为的模拟。这种强有力控制的现代模拟将成为预测未来行为的实验的起点。该项目的结果将是确定在几十年、几百年、几千年或冰川周期的时间尺度上，不断演变的基底地形对冰流稳定性是否重要。同样，它可以确定，尽管侵蚀和沉积是广泛存在的过程，但对冰流的行为没有显著影响。这些结果中的任何一个的建立都将是一个重大的好处，使未来的冰流稳定性研究能够适当地纳入不断变化的基础条件。因此，这个项目将完善我们对控制冰流行为的因素的理解，从而提高在全球变暖背景下的预测能力。

The future stability of the Antarctic and Greenland Ice Sheets is important due to the risk of sea-level rise in a warming climate. However, the controls on ice sheet behavior are not fully understood. One potential control that has received less attention than it should is the importance of continuously evolving bed topography. This study aims to test how ice sheets respond to patterns of evolving subglacial topography via the processes of glacial erosion and deposition. Observations suggest that erosion and deposition can rapidly and significantly change the shape of the landscape under the ice. These changes may have an impact on the behavior of the overlying ice on timescales of decades to centuries and beyond. For example, geological data and theory suggests that erosion may destabilise ice streams and lead to rapid ice sheet retreat whereas deposition may enable an ice stream to stabilise or advance. The approach of this project is to construct a computer model that integrates the ability to erode and deposit sediment underneath an ice stream, with the ability to monitor how the ice stream responds. Such a model has not been developed before, despite the potential importance of erosion and deposition to control the sensitivity of an ice-sheet to changes in climate or sea level. This project therefore targets a potentially critical question for future ice-sheet behavior. It is made possible by the collection of significant volumes of data that help quantify how fast, and in what pattern erosion and deposition can occur. These data, provided by collaborators from all over the world, can be used to control the model so that realistic, robust and repeatable simulations can be carried out. This is important for having confidence in the model's ability to capture and predict the real sensitivity of ice streams to different control factors.The model will be used to ask 3 key questions:1) Can the deposition of wedges of sediment at the transition between grounded and floating ice stabilise ice streams against future sea-level rise and climate warming?2) Can glacial erosion drive ice stream retreat, and if so, over what timescales?3) How might the Whillans Ice Stream in West Antarctica respond to erosion and deposition in the future as sea levels rise and the climate warms?The Whillans Ice Stream is used here as a test-case because it is the focus of a major effort to understand the subglacial conditions of an ice stream. As a result, it is one of the best monitored modern systems, with data on ice flow, basal erosion and deposition that will be used to construct a simulation of present-day behavior. This robustly controlled modern simulation will form the starting point for experiments that go on to predict future behavior. The outcome of this project will be to identify whether evolving basal topography is important for ice stream stability on timescales of decades, centuries, millennia or glacial cycles. Equally, it may identify that erosion and deposition, despite being widespread processes, do not significantly impact upon ice-stream behavior. The establishment of any of these outcomes will be a significant benefit, enabling future studies of ice stream stability to incorporate evolving basal conditions as appropriate. As a result, this project will refine our understanding of what controls ice stream behavior and thereby improve predictive capabilities in the context of a warming world.