Aufeis is a sheet-like mass of layered ice

Ice

Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 that forms from successive flows of ground water during freezing temperatures. This form of ice is also called overflow, icings, or the Russian

Russian language

Russian is a Slavic language used primarily in Russia, Belarus, Uzbekistan, Kazakhstan, Tajikistan and Kyrgyzstan. It is an unofficial but widely spoken language in Ukraine, Moldova, Latvia, Turkmenistan and Estonia and, to a lesser extent, the other countries that were once constituent republics...

 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

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

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Formation

Aufeis accumulates during winter along stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

 and river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 valley

Valley

In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

s in arctic

Arctic

The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 and subarctic

Subarctic

The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, the north of Scandinavia, Siberia, and northern Mongolia...

 environments. It forms by upwelling of river water behind ice dam

Ice dam

An ice dam occurs when water builds up behind a blockage of ice. Ice dams can occur in various ways.-Caused by a glacier:Sometimes a glacier flows down a valley to a confluence where the other branch carries an unfrozen river...

s, or by ground-water discharge. The latter mechanism prevails in high-gradient alpine

Alpine climate

Alpine climate is the average weather for a region above the tree line. This climate is also referred to as mountain climate or highland climate....

 streams as they freeze

Freezing

Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 solid. Ground-water discharge is blocked by ice, perturbing the steady-state condition and causing a small incremental rise in the local water table

Water table

The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

 until discharge occurs along the bank and over 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 often form in the same place year after year.

Impact

Sheets of aufeis may block stream channels and cause their flood plains to widen as spring floodwaters are forced to flow around the ice. 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). Culvert

Culvert

A culvert is a device used to channel water. It may be used to allow water to pass underneath a road, railway, or embankment. Culverts can be made of many different materials; steel, polyvinyl chloride and concrete are the most common...

s and pipelines can actually help to block flow and lead to the development of more extensive aufeis.

City cooling

In late 2011, Mongolia will test the use and storage of artificial naleds as a way of cooling Ulan Bator in the hot Mongolian summer, and reducing the use of energy-intensive air conditioning

Air conditioning

An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...

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Occurrence

Sheets of aufeis have been observed in Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

,, Arctic Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, and Mongolia

Mongolia

Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

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