iSTAR-C - Dynamical control on the response of Pine Island Glacier

预计海平面上升将在未来几十年到几个世纪内影响全世界的沿海社区。在英国，沿海社区和资产的脆弱性最好体现在海防可能出现的频率上。例如，伦敦市的海防工事（包括泰晤士河水闸）在建造时，是为了保护伦敦免遭千年一遇的洪水。全球海平面上升50厘米将使这一保护水平减少到1-100年，上升100厘米将使其减少到1-10年。松岛冰川是西南极洲的五个冰川之一，它们目前正以显著且加速的速度导致海平面上升。受变薄影响的部分海流所含的冰足以使全球海平面上升约25厘米——其邻近地区的冰又会使海平面上升50厘米。考虑到冰的损失率和对海防规划的潜在影响，我们显然需要了解和预测松岛冰川及其邻近地区的未来。然而，正如政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, 2007）所强调的那样，人们对动态变化通过冰川流失冰盖的方式传播的了解甚少，以至于政府间气候变化专门委员会（IPCC）认为，这是对下个世纪海平面上升的最不了解的，也可能是最大的贡献。ISTAR-C将通过寻求了解负责向上游传播浮冰架变薄影响的过程，从而在松岛冰川的大部分干流和支流上可以看到变薄，从而直接解决这一知识缺乏问题。ISTAR-C还将使用现有的最先进的方法来测量松岛冰川几个地点下面的床的性质（岩石类型和含水量），以确定它们对变薄传播的影响。我们将测试这样一个假设，即这些床条件是造成松岛冰川支流似乎以不同的速度变薄的原因，这将使我们更好地了解如何预测冰川未来冰变薄速度的大小。为了实现这些目标，我们将在两个野外季节收集松树岛冰川的数据。这将包括精确测量从冰架到冰川再到支流的冰流的变化。我们将利用雷达和地震技术对冰川床进行成像，在地面无法进入的地区，利用卫星测量冰川的变化形态。我们将利用收集到的数据来驱动和验证一套松岛冰川动态的计算机模拟。每一个都将测试冰川流动的一个特定方面，并允许我们根据实际数据测试我们目前的知识和假设。由此产生的模型在模拟冰川过去的变化方面显然更加可靠，从而减少了预测这种变化的未来演变及其对海平面上升的影响的不确定性。总的来说，这个项目将大大提高人们对冰川与冰川床的相互作用的理解，并提供关于地球上变化最快、最重要的冰川之一——松岛冰川的非常具体的课程。

It is expected that sea-level rise will impact coastal communities worldwide over the coming decades to centuries. In the UK, the vulnerability of coastal communities and assets is best characterised in terms of the likely frequency of the over-topping of sea-defences. For example, when they were built, the sea-defences for the city of London (including the Thames Barrier) were designed to protect London 1-in-1000 year flooding. A rise of 50 cm in global sea level will reduce this level of protection to 1-100 years, and a rise of 100 cm would reduce it to 1-in-10 years. Pine Island Glacier is one of five glaciers in West Antarctica that are currently contributing sea-level rise at a significant and accelerating rate. The portion of current affected by thinning contains sufficient ice to raise global sea-level by around 25 cm - its neighbours account for another 50 cm. Given the rate of ice-loss and the potential implications for sea-defence planning there is a clear requirement to understand and predict the future of Pine Island Glacier and its neighbours. However, as highlighted by the Intergovernmental Panel on Climate Change (2007) understanding the way that dynamic changes are transmitted through the glaciers draining ice sheets is so poorly understood that the IPCC believed it was the least well understood, and potentially the largest, contribution to sea-level rise in the coming century.ISTAR-C will directly address this lack of knowledge, by seeking to understand the processes that are responsible for transmitting the effect of thinning of the floating ice shelf, upstream such that thinning can now be seen on much of the trunk and tributaries of Pine Island Glacier.ISTAR-C will also use the most up-to-date methods available to measure the properties (rock-type and water-content) of the bed beneath at several locations on Pine Island Glacier to determine their influence on the propagation of thinning. We will test the hypothesis that it is these bed conditions are responsible for the fact that the tributaries of Pine Island Glacier appear to be thinning at different rates, which will give us a much better understanding on which to predict the future magnitudes of ice-thinning rates for the glacier. To achieve these objectives we will collect data from Pine Island Glacier during two field seasons. These will include precise measurement of variations in ice-flow from the ice-shelf up the glacier and into its tributaries. We will image the bed of the glacier using radar and seismic techniques, use satellite to measure the changing configuration of the glacier in areas that cannot be accessed on the ground. We will use the data we have collected to drive and verify a set of computer simulations of the dynamics of Pine Island Glacier. Each of these will test a particular aspect of the glacier flow, and allow us to test our current knowledge and hypotheses against real data. The models that emerge from the exercise will be demonstrably more reliable in simulating past changes on the glacier, and thus have reduced uncertainty in predicting the future evolution of such changes, and the consequential contribution to sea-level rise.Overall, this programme will deliver significant improvements in understanding of how glaciers in general interact with their beds, and very specific lessons about one of the most rapidly-changing and significant glaciers on the planet, Pine Island Glacier.