Models and observational constraints for fast ice flow and marine ice sheet dynamics

格陵兰岛和南极洲西部的冰原所含的淡水足以使全球海平面上升约13米。目前，还没有可靠的预测，这些冰盖在预计的气候变化下会以多快的速度萎缩，而且无法准确预测未来海平面上升的速度。要想更好地预测冰盖的行为，就需要在数值模型中更准确地表示许多物理过程。冰盖并不是均匀流动的，而是包含着被称为冰流的快速流动通道。这些冰流是如何形成、演变并最终再次关闭的，我们只是部分地了解，而且其中的许多物理原理在目前的冰盖模型中没有得到体现。同样地，控制冰盖边缘（从而控制其水平范围）演变的物理学也只是部分地被理解。特别是，格陵兰岛和南极冰盖的边缘在许多地方是由冰开始漂浮并形成冰架的位置确定的。目前的模型无法准确预测冰流过冰原和冰架连接处的速度，从而阻碍了对未来海平面变化的估计。拟议的研究计划将通过解决涉及冰流流动和冰盖边缘演变的基本物理问题，针对当前冰盖模型中的这些弱点。该研究项目将采取双管齐下的方法，使用复杂的现代数学方法，结合一个新的实地项目的数据，得出用于数值模拟的冰盖物理的改进表示。

The ice sheets of Greenland and West Antarctica contain sufficient fresh water to raise global sea levels by about 13 metres. At present, there are no reliable predictions of how fast these ice sheets may shrink under projected climate change, and the future rate of sea level rise cannot be forecast accurately. Better predictions of ice sheet behaviour will require a number of physical processes to be represented more accurately in numerical models. Ice sheets do not flow evenly, but contain channels of fast flow known as ice streams. How these ice streams form, evolve and ultimately shut down again is only partially understood, and much of the physics involved is not represented in currebt ice sheet models. Similarly, the physics that controls the evolution of the edges of ice sheets (and hence their horizontal extent) is only partially understood. In particular, the edges of the Greenland and Antarctic ice sheets are defined in many places by the location where ice begins to float and forms an ice shelf. The rate at which ice flows through these junctions between ice sheets and ice shelves cannot be predicted accurately by present models, hampering efforts to estimate future sea level changes. The proposed research program will target these weaknesses in current ice sheet models by addressing the fundamental physics involved in ice stream flow and in the evolution of the margins of ice sheets. The research program will take a two-pronged approach, using sophisticated modern mathematical methods in conjunction with data from a new field program to derive improved representation of ice sheet physics for use in numerical simulations.