Observations and Modelling of Freeze-up Processes in Rivers

当北方河流的水过冷到零下时，在湍流部分形成了微小的冰颗粒，称为“冰冻”。几乎所有形式的河冰都起源于巴西，它的形成和演变是冻结期间主要的河冰过程。巴西颗粒在过冷水中很容易附着在天然和人造表面上。它们可能会粘在床上，形成锚冰，或者彼此粘在一起，形成絮凝体，最终在表面变成大的泥球，在一起冻结成“巴西平底锅”，最终形成冰盖。数值河冰模型包括模拟冻结过程的算法，但由于缺乏实地数据进行比较，其准确性尚不清楚。虽然近年来在发展精确的测量技术方面取得了进展，但仍然非常需要额外的实地测量。为了满足这一需求，我提出了一个雄心勃勃的实地测量计划，旨在显著增加我们对关键冻结过程的了解，并使用所得数据来评估目前用于模拟这些过程的算法的准确性。这项研究的长期目标是提高我们对河流冰如何形成及其对河流生态、水力学和地貌的影响的理解。该研究计划的短期目标是：(1)继续研究河流中悬浮冰的产生、运输和命运(2)研究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在拟议的研究中合作。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模拟的培训。实地测量将在两条河流上进行多个冬季。River1D是一个河流冰过程模型，将应用于两条河流，其模拟冻结过程的准确性将通过比较模型预测和现场测量来评估。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对其进行分析。他们的目标是准确估计释放的锚冰带所携带的沉积物数量。提高对河流冰冻过程的准确监测和预测能力，将对沿河基础设施的规划、设计、建设和运营产生重大影响。它还将提高我们评估寒冷地区项目对环境影响的能力，并更准确地评估气候变化对北方河流冻结过程的影响。

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.