Aufeis
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Aufeis (German for "ice on top") is a sheet-like mass of layered ice that forms from successive flows of ground water during freezing temperatures. This form of ice is also called icings or, by the Russian term, naled. According to E. de K. Leffingwell the term was first used in 1859 by A. T. von Middendorff following his observations of the phenomenon in northern Siberia.
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[edit] Formation of aufeis
Aufeis accumulates during winter along stream and river valleys in arctic and subarctic environments. Aufeis forms by upwelling of river water behind ice dams, or by ground-water discharge. The latter mechanism prevails in high-gradient alpine streams as they freeze solid. Ground-water discharge is blocked by ice, perturbing the steady-state condition, and causing a small incremental rise in the local water table until discharge occurs along the bank at the top of the previously formed ice. Successive ice layers can lead to aufeis accumulations that are several meters thick. Aufeis typically melts out during summer and will form in the same place year after year (Hu and Pollard, 1997).
[edit] Humans and aufeis
Sheets of aufeis may block stream channels and cause their flood plains to widen as spring floodwaters are forced to flow around the ice (Harden et al., 1977). Research on aufeis has to a large extent been motivated by the variety of engineering problems the ice sheets can cause (e.g. blocking drainages and causing flooding of roads) (Kane 1981). Culverts and pipelines can actually help to block flow and lead to the development of more extensive aufeis (Williams and Smith, 1989).
[edit] Occurrence of aufeis
Sheets of aufeis have been observed in Alaska (Harden et al., 1977; Kane, 1981), Arctic Canada (Veillette and Thomas, 1979; Reedyk et al., 1995; Clark and Lauriol, 1997; Priesnitz and Schunke, 2002), Russia (Sokolov, 1978) and Mongolia (Froelich, 1982; Swanson-Hysell and Dandar, 2005).
[edit] References
- Clark, I., and Lauriol, B., 1997, Aufeis of the Firth River basin, northern Yukon Canada: Insights into permafrost hydrogeology and karst: Arctic and Alpine Research, v. 29, no. 29, p. 240-252.
- Froehlich, W., and Slupik, J., 1982, River icings and fluvial activity in extreme continental climate: Khangai Mountains, Mongolia: Proceedings, 4th Canadian Permafrost Conference, p. 203-211.
- Harden, D., Barnes, P., and Reimnitz, E., 1977, Distribution and character of naleds in northeastern Alaska: Arctic, v. 30, no. 1, p. 28-40.
- Hu, X., and Pollard, W., 1997, The hydrologic analysis and modeling of river icing growth, North Fork Pass, Yukon Territory, Canada: Permafrost and Periglacial Processes, v. 8, p. 279-294.
- Kane, D., 1981, Physical mechanics of aufeis growth: Canadian Geotechnical Journal, v. 8, no. 2, p. 186-195.
- Priesnitz, K., and Schunke, E., 2002, The fluvial morphodynamics of two small permafrost drainage basins, northwestern Canada: Permafrost and Periglacial Processes, v. 13, no. 3, p. 207-217.
- Reedyk, S., Woo, M., and Prowse, T., 1995, Contribution of icing ablation to streamflow in a discontinuous permafrost area: Canadian Journal of Earth Sciences, v. 32, no. 1, p. 13-20.
- Sokolov, B. L., 1978, Regime of naleds: Permafrost: the USSR contribution to the Second International Conference, National Academy of Sciences, p. 408-411.
- Swanson-Hysell, N. and Dander, E., 2005. Aufeis in the Kharkhiraa Uul. Eighteenth Annual Keck Research Symposium in Geology Proceedings http://keck.wooster.edu/publications/2005_abstracts/mongolia/10swansonAbstractFinal.pdf
- Veillette, J., and Thomas, R., 1979, Icings and seepage in frozen glacio-fluvial deposits, District of Keewatin, NWT: Canadian Geotechnical Journal, v. 16, no. 4, p. 789-798.
- Wanty et al, Aufeis Accumulations in Stream Bottoms in Arctic and Subarctic Environments as an Indicator of Geologic Structure
- Leffingwell, E. de K., 1919, The Canning River region, northern Alaska: U.S. Geological Survey Professional Paper 109, 251 p., 6 sheets, scale 1:125,000.
