Ground ice
Grundeis is forming on the base of running water ice. It grows from the bottom of the water into the water and sometimes forms bizarre underwater sculptures.
Emergence
Ground ice only occurs during persistent periods of severe frost and certain bodies of water. It forms when the ground freezes deeply during permanent frost and temperatures below 0 ° C are then also reached in the river bed. While the surface of stagnant water cools down first and the first ice forms there, in flowing water there is a constant mixing of the water, and the ice forms first where the water is calmest, i.e. at the bottom and on the banks. In 2012, however, it was observed in the Steinach Valley near Kulmbach that the ground ice formation ultimately only required a small connection to the bottom of the brook in order to then emerge "like a bulb" in the current-rich water (Mühlgraben).
Another prerequisite for the formation of ground ice is that there is no connection between the body of water and the groundwater, i.e. only little water seeps away or groundwater flows through the bed into the body of water, because groundwater penetrates from deeper layers of earth and rock and is therefore warmer than 0 ° C , thereby preventing the freezing of the water bottom .
hazards
Ice has a lower density than liquid water . The ground ice thus has static buoyancy . As the volume increases, it can detach from the ground and rise. Then it forms drift ice , usually carrying mud and gravel with it . The suddenly increased amount of ice can in turn lead to ice congestion .
Since ground ice reduces the depth of the river, this can lead to problems for shipping as the fairway may become too shallow. In addition, due to the reduced cross-section of the flowing water, even with normal water flow, the water can overflow its banks and cause widespread flooding. This happened, for example, decades ago at the Hachinger Bach .
Individual evidence
- ↑ a b Frost curiosity: brooks freeze from the bottom ( PDF , 37 kB) - press release of January 13, 2009 by the Bavarian State Office for the Environment
