In the present climate, almost all high-latitude rivers in northern regions freeze every winter. In the future, however, climate change may cause shifts in freezing, duration and breakup of river ice cover, runoff, and sediment transport. The main aim of the study is to determine changes in surface flow velocity during river ice freezing and melting periods. We also examine the interplay between surface flow velocity and the initiation and progress of freezing and break-up. The study was performed in three Nordic rivers: the Pulmanki (northern Finland), the Koita (eastern Finland), and the Sävar (northern Sweden). They represent different slope and depth conditions and are representative of boreal and sub-arctic channel types. The flow characteristics were measured and remote sensing data for video-based surface velocimetry analyses (STIV) were collected during one season in each river during autumn ice-formation and spring ice break-up. STIV enabled analyses of surface flow velocities, which were compared to direct flow measurements and against freezing (incl. frazil ice, and partial ice cover) and break-up characteristics.

中文翻译：

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北欧河流冰冻融期的表面流和冰筏漂流速度


在目前的气候下，北方地区几乎所有的高纬度河流每年冬天都会结冰。然而，在未来，气候变化可能会导致河流冰盖、径流和沉积物运输的冻结、持续时间和破裂发生变化。该研究的主要目的是确定河冰冻结和融化期间表面流速的变化。我们还研究了表面流速与冻结和破裂的开始和过程之间的相互作用。该研究在三条北欧河流进行：普尔曼基河（芬兰北部）、科伊塔河（芬兰东部）和萨瓦尔河（瑞典北部）。它们代表不同的坡度和深度条件，代表北方和亚北极河道类型。在秋季结冰和春季冰破裂期间，测量了流动特征，并收集了每条河流一个季节的基于视频的表面测速分析 （STIV） 的遥感数据。STIV 能够分析表面流速，将其与直接流动测量以及冻结（包括 frazil 冰和部分冰盖）和破裂特性进行比较。