Author(s): Hirotaka Suzuki; Masahiro Hashiba; Yasuhiro Yoshikawa; Hiroshi Yokoyama
Linked Author(s): Hiroshi Yokoyama
Keywords: No keywords
Abstract: Anchor ice is a phenomenon to accumulate of frazil ice on the river bed. This is formed due to the super cooling and a shallow, turbulent section of the river. In this study we observed a continuous observation of air temperature, water temperature, stone temperature, water level in Syuku-syu-betsu River and Yubetsu River, and we could successfully capture from the occurrence to the disappearance of anchor ice using the underwater video camera. The anchor ice began to occur from riverbed in early morning and spread to the ground area while increasing the thickness and finally covered with the riverbed stone. When the sunshine was getting strong, the anchor ice gradually became thin and disappeared. As a result, Firstly, we found the critical element of the anchor ice occurrence-disappearance was keeping supercooling condition. Secondary, it was found when the temperature of the stone was rising above the water temperature due to influence of sunshine, the anchor ice disappeared. On the other hand, we attempted to analyze two-dimensional flow calculation and spatial distribution of photo image analysis of an anchor ice. As a result, we found spatial distribution of anchor ice was proportional to the Froude number. Next to we conducted the impact of anchor ice on material transport in ice-covered river. We analyzed the contained algae of an anchor ice. As a result, a lot of algae (diatoms) existed in the anchor ice. When the one day cycle (occurrence and disappearance) of anchor ice repeated, the algae biomass tended to decrease. The reason for this phenomenon was considered that the growth rate of algae was shorter than the one-day cycle of the anchor ice.
Year: 2018