Predicting Dynamic River Ice Processes

河冰是加拿大的一个重要问题，就像在许多其他北方国家一样。与典型的仲冬冰盖所暗示的和平形象相反，河冰实际上是由各种各样的动态过程组成的，特别是在冻结和破裂期间，这些动态冰过程可能会造成重大问题。例如，在秋天，当水温冷却到零下百分之几度时，“frazil冰”颗粒就会形成。这些微小的冰粒最初通过流体湍流悬浮在整个河流中。然而，frazil行为在一个非常'粘'的方式在这sucoled水，并很容易坚持自己和许多其他物体。它可以附着在进水口的滤网和垃圾架上，切断市政、工业和发电厂的供水。它还可以粘在河床上，形成“锚冰”，这对鱼类非常有害。例如，在小河流中，锚冰可以在一夜之间填满整个河道，抑制幼鱼的栖息地，或阻止埋藏在河床中的卵的氧气供应。春季的河流结冰同样会带来问题。在断裂特别活跃的河流上，冰塞可能会形成，导致洪水泛滥，并对人类安全构成重大威胁。能够预测这些和其他动态冰过程是很重要的，这样我们就可以计划取水口的有效运作，以避免产生锚冰问题（特别是在河流栖息地恢复项目中），并为公众提供即将发生的洪水的充分警告。然而，目前，可用于预测河冰过程的数值模型的某些组件实际上是高度经验性的或尚未得到严格验证。一些冰的特性（例如悬浮的冰浓度）甚至还不能测量。因此，我们并不总是知道模型是否“正确”。这项研究的重点是进行各种动态河冰过程的实地研究，旨在提高我们的知识和能力，实施更多的物理基础的数值模型，并提供必要的验证数据来测试这些预测模型。

River ice is an important issue in Canada, as in many other northern countries. Contrary to the peaceful image that the typical mid-winter ice cover implies, river ice is actually comprised of a broad variety of dynamic processes, particularly during freeze-up and breakup, and these dynamic ice processes can cause significant problems. For example, in the fall as water temperatures cool to a few hundredths of a degree below zero, "frazil ice" particles form. These tiny ice particles are initially suspended throughout the river flow by fluid turbulence. However, frazil behaves in a very 'sticky' manner in this supecooled water and readily sticks to itself and many other objects. It can attach to screens and trash racks on water intakes, cutting off the water supplies to municipalities, industries, and power plants. It can also stick to the river bed, building up "anchor ice", which can be very harmful to fish. For example, in small rivers, anchor ice can fill up the entire channel in a single night, inhibiting habitat access for juvenile fish or blocking the oxygen supply to eggs buried in the stream bed. River ice can be equally problematic in spring. On rivers where the breakup is particularly dynamic, ice jams can form causing flooding and presenting a significant threat to human safety. It is important to be able to predict these, and other, dynamic ice processes so that we can plan the effective operations of water intakes, to avoid creating anchor ice problems (particularly in stream habitat restoration projects), and to provide the public with adequate warning of impending floods. However, at present, certain components of the numerical models available to predict river ice processes are actually highly empirical or not yet rigorously validated. Some ice properties (for example, suspended frazil concentrations) cannot yet even be measured. Therefore, we don't always know if the models are 'getting it right'. This research is focused on conducting field studies of a variety of dynamic river ice processes, aimed at advancing our knowledge and ability to implement more physically based numerical models, and to provide essential validation data to test these predictive models.