Observations and Modelling of Freeze-up Processes in Rivers

在北方河流中，当水流过冷到零度以下时，在湍流部分形成了微小的冰粒，称为冰粒。几乎所有形式的河冰都起源于冰碛，冰碛的形成和演变是河冰封冻过程中的主要过程。过冷水中的碎冰颗粒很容易粘附在自然和人造表面上。它们可能会粘在冰床上，形成锚冰，或者相互粘在一起，形成絮状物，最终在表面变成大的雪泥球，冻在一起形成“冰盘”，最终形成冰盖。数值河冰模型包括模拟冻结过程的算法，但由于缺乏现场数据进行比较，其准确性是未知的。虽然近年来在开发精确测量技术方面取得了进展，但仍然非常需要进行更多的实地测量。为了满足这一需求，我提出了一个雄心勃勃的计划，旨在显着增加我们的知识的关键冻结过程的现场测量，并使用由此产生的数据来评估目前用于模拟这些过程的算法的准确性。拟议研究的长期目标是提高我们对河冰如何形成及其对河流生态，水力学和地貌的影响的理解。拟议研究计划的短期目标是： （1）继续调查河流中悬浮冰的产生、运输和归宿 （2）调查锚冰的性质及其对河流生态和水力学的影响。 （3）确定锚冰漂流泥沙对河流泥沙收支的影响。 （4）评估河冰过程模型准确模拟冻结的能力。 三名博士和两名硕士学生将合作进行拟议的研究。学生将接受有关使用各种复杂现场仪器、先进数据处理方法和数值建模的培训。实地测量将在两条河流的多个冬季进行。River1D是一个河流冰过程模型，将应用于这两条河流，并通过将模型预测与现场测量结果进行比较来评估其模拟冻结过程的准确性。理学硕士学生将收集和平河表面冰况的数字图像，并使用机器学习技术进行分析。他们的目标是获得释放的锚冰盘所输送的沉积物数量的准确估计。提高我们准确监测和预测河流封冻过程的能力将对沿着建设的基础设施的规划、设计、建设和运营产生重大影响。它还将提高我们评估寒区项目的环境影响的能力，并更准确地评估气候变化对北方河流封冻过程的影响。

Tiny ice particles, called frazil, form in the turbulent portions of the flow in northern rivers when the water supercools to just below zero degrees. Virtually all forms of river ice originate from frazil and its formation and evolution are the dominant river ice processes during freeze-up. Frazil particles in supercooled water readily adhere to natural and man-made surfaces. They may stick to the bed, forming anchor ice, or to each other, creating flocs that ultimately become large slush balls at the surface, freeze together into `frazil pans,' and eventually form the ice cover. Numerical river ice models include algorithms for simulating freeze-up processes but their accuracy is unknown due to a lack of field data to compare with. Although progress has been made in recent years to develop accurate measurement techniques there is still a great need for additional field measurements. To address this need, I propose an ambitious program of field measurements designed to significantly increase our knowledge of key freeze-up processes, and to use the resulting data to assess the accuracy of the algorithms currently used to model these processes. The long-term goal of the proposed research is to improve our understanding of how river ice forms, and its impacts on river ecology, hydraulics, and geomorphology. The short-term objectives of the proposed research program are to:    (1)Continue investigating the generation, transport, and fate of suspended frazil ice in rivers    (2)Investigate the properties of anchor ice and its impact on the ecology and hydraulics of rivers.    (3)Determine the impact of rafting of sediment by anchor ice on the sediment budget of rivers.    (4)Assess the ability of river ice process models to accurately model freeze-up. Three PhD and two MSc students will collaborate on the proposed research. The students will receive training on the use of a wide variety of sophisticated field instrumentation, advanced data processing methods and numerical modelling. Field measurements will be conducted over multiple winters on two rivers. River1D, a river ice processes model, will be applied to both rivers and its accuracy simulating freeze-up processes will be assessed by comparing model predictions to field measurements. The MSc students will gather digital images of surface ice conditions on the Peace River and analyze them using machine learning techniques. Their goal is to obtain accurate estimates of the amount of sediment transported by released anchor ice pans. Improving our ability to accurately monitor and predict freeze-up processes in rivers will have a significant impact on the planning, design, construction and operation of infrastructure built along rivers. It will also enhance our ability to assess the environmental impacts of cold region projects and more accurately assess the impact of climate change on freeze-up processes in northern rivers.