The role of snow and ice thickness on river ice process in Songhua River basin, Northeast China
Abstract. Songhua River basin is a sensitive area to global warming in Northeast China that could be indicated by changes in lake and river ice development. The regional role and trends of ice characteristics of this area have been scarcely investigated, which are critical for aquatic ecosystem, climate variability, and human activities. Based on the ice record of hydrological stations, we examined the spatial variations of the ice phenology and ice thickness in Songhua River basin in Northeast China from 2010 to 2015 and explored the role of ice thickness, snow during ice on and ice off process. All five river ice phenology including freeze up start, freeze up end, break up start, break up end and complete frozen duration showed latitudinal distribution and a changing direction from southeast to northwest, and five typically geographic zones were identified based on rotated empirical orthogonal function. Maximum ice thickness had a higher correlation with five parameters than that of average snow depth and air temperature on bank. A linear regression function was established between ice thickness and snow depth on ice and indicated ice thickness was closely associated with snow depth on ice. The air temperature had higher correlation with ice phenology and influenced the lake ice phenology significantly, and snow cover did not show significant correlation with the ice phenology. However, snow cover correlated with ice thickness significantly and positively during the periods when the freshwater is completely frozen.