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Stratification and Heat Transfer in Lakes and Reservoirs
Published in James L. Martin, Steven C. McCutcheon, Robert W. Schottman, Hydrodynamics and Transport for Water Quality Modeling, 2018
James L. Martin, Steven C. McCutcheon, Robert W. Schottman
In flowing water bodies, such as rivers and streams where vertical mixing is sufficient to transport supercooled water beneath the surface, ice crystals may form at depth. The resulting ice crystals are referred to asfrazil ice. Frazil ice consists of small plate-like crystals that are produced throughout the flow (Ashton 1982). Frazil ice in supercooled water is not at equilibrium and the ice crystals usually continue to grow as they are carried downstream. The crystals may flocculate and rise to the surface. Also, frazil ice readily attaches to surfaces, often coating aquatic vegetation, submerged objects, the underside of ice sheets, and the benthos. A coating of frazil ice on the bottom of a lake is called anchor ice.
Ecology of Sea Ice Microalgae
Published in Rita A. Horner, Sea Ice Biota, 1985
Anchor ice is important because it provides a means by which benthic organisms can be transported to the under surface of the ice and because sediment transported by it and subsequently incorporated into the ice cover increases turbidity in the ice and decreases light penetration that could affect algal growth.48 Little is known about anchor ice, including factors that govern its formation such as water depth (but see Dayton et al.21), circulation patterns, salinity, or bottom substrates.48
Anchor-ice rafting, an important mechanism for bed-sediment transport in cold-regions rivers
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
E.W. Kempema, R. Ettema, K. Bunte
Channels with large width/depth ratios usually have slopes >10-3. The morphology of such channels reflects the action that slope exerts in increasing flow velocity (e.g. as expressed by Manning’s equation). Increased velocity and decreased flow depth promote anchor ice growth during the onset of frigid weather. However, even nominally still water bodies (e.g. lakes) subject to wind- or wave-generated turbulent mixing can form anchor ice and raft bed sediment.
Effects of climate change on river-ice processes and ice jams
Published in International Journal of River Basin Management, 2023
B. C. Burrell, S. Beltaos, B. Turcotte
Anchor ice is porous, submerged ice attached to the riverbed, irrespective of the nature of its formation (IAHR, 1980), which includes local crystal growth as well as turbulent transport and adherence of suspended frazil particles, flocs, or snow slush (Malenchak & Clark, 2013; Turcotte et al., 2012a) to the riverbed. Channels with large aspect ratios (channel width/average depth of channel) can respond quickly to heat fluxes and thereby can produce large quantities of anchor ice (Kempema et al., 2020). Due to a combination of solar heating, flow fluctuations, and an increase in buoyancy, anchor ice can lift off the bed into the flow, often carrying bed material and vegetation with it. In small and steep rivers, anchor ice can form uninterruptedly over several consecutive days, leading to the formation of large ice dams, i.e. bottom-fast anchor-ice accumulations spanning the stream width and becoming partially emergent (Dubé et al., 2014; Turcotte et al., 2011b). Successive ice dams, developing at a rate of 0.5–2.0 vertical cm per hour, generate series of slow flowing channel segments where a surface ice cover can form (Dubé et al., 2015; Turcotte et al., 2013).
Ice in reservoirs and regulated rivers
Published in International Journal of River Basin Management, 2022
Mikko Huokuna, Mike Morris, Spyros Beltaos, Brian C. Burrell
Many northern rivers and lakes are strongly or moderately affected by regulation, with hydropower production being the main reason for river regulation. Dams and other forms of river regulation create unnatural river stretches in naturally free-flowing rivers and streams, causing changes in river water levels, flow, sediment movement and deposition, ecology, and ice transport. Regulation alters river ice regimes by modifying the temporal and spatial characteristics of flow, water level, and thermal regimes in a watercourse. Frazil ice, anchor ice, ice runs, and ice jams can cause structural damage to infrastructure, flooding, harm to ecosystems, and operational restraints at water works and hydropower plants, resulting in significant economic losses. Removal of a dam or other water control structure can eliminate some ice problems, but create new problems in areas where environmental or development conditions have changed.