Hydrological and thermal controls of ice formation in 25 boreal stream reaches
(English)Manuscript (preprint) (Other academic)
The Northern Hemisphere has a high density of fluvial freshwater ecosystems, many of which become ice-covered during winter. The formation and extent of ice have both ecological and socio-economic implications. For example, ice can cause freezing of riparian vegetation and fish eggs as well as influence hydropower production; however, when, where and why ice develops in small streams is poorly described. Data from 25 stream reaches were used to study the factors controlling ice formation during two consecutive winters. We addressed where in the catchment surface or anchor ice is most likely to develop, how stream morphology influences ice formation, and how climate influences ice processes. Reaches far away from lake outlets were most prone to form anchor ice, but many other factors also influenced ice formation. We found that anchor-ice was most common where water temperature and groundwater input were low and stream power high. The in-stream substrate was also important for the formation of anchor ice as well as the current velocity, which created turbulence and super-cooled conditions if high enough. We demonstrated that ice formation in the studied streams was complex, involving many variables, thus we constructed a conceptual model describing the likelihood of various ice types to develop, based on our large dataset. To our knowledge, this model is the first to describe the complexity of ice formation in steep boreal streams. As such it will be useful for practitioners and scientists working in small rivers in the Northern Hemisphere.
anchor ice, boreal, channel morphology, groundwater, ice, river ice, stream
Earth and Related Environmental Sciences Oceanography, Hydrology, Water Resources
IdentifiersURN: urn:nbn:se:umu:diva-99003OAI: oai:DiVA.org:umu-99003DiVA: diva2:785098
FunderSwedish Research Council Formas