And Rivers

Sheets or stretches of ice also form on the surface of lakes and rivers when the temperature drops below freezing (0 C 32 F ). The nature of the ice formations may be as simple as a floating layer that gradually thickens, or it may be extremely complex, particularly when the water is fast-flowing. Much of the world experiences weather well below the freezing point, and in these regions ice forms annually in lakes and rivers. About half the surface waters of the Northern Hemisphere freeze...

R

Railroads, in permafrost areas, 52 randkluft, i27 regelation, 83, i2i regenerated reconstituted glaciers, 84 rime, 25, 79, i02 rivers, ice in, 53, 64-73 accumulating ice cover, 65-67 geographic distribution of, growth of fixed ice cover, 67 ice buildups, 67-69 ice decay and, 69 ice jams and, 69-70, 71 modification of, 70-71 seasonal cycle of, 53-54 supercooling and, 64, 65 roche moutonn es, 131, 132 rock drumlins, 124, 131, 132, 138 rock glaciers, 47, 96, 144 rock polish, 124-125 Ross, James...

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Geothermal gradient, 31, 32, 35 geothermal heating, 30, 31, 33 glacial deposition, 121-124, 127, causes of, I24 glacial fluctuations, 74-75, II3 glacial grooves, I24, I26 glacial lakes, I4I-I43 glacial landforms, 116-144 Glacier Bay, 97 glacier floods, 93-94 glacier ice, formation of, 76-78 ghti s 74-97 classification of, 74, 79-80 continental, 2I, 89, II8, I3I-I35, 113-114 geographic distribution of, 75, 97 i93-i96 heat energy balance and, 80-8i hydrology of, 92-93 icebergs and, i45, i48...

Types Of Ground

The ice content of permafrost is probably the most important feature of permafrost affecting human life in the north. Ice in the perennially frozen ground exists in various sizes and shapes and has definite distribution characteristics. The forms of ground ice can be grouped into five main types pore ice, segregated (or Taber) ice, foliated (or wedge) ice, pingo ice, and buried ice. Pore ice, which fills or partially fills pore spaces in the ground, is formed by pore water freezing in situ with...

Sea Ice Formation and Features

Sea ice that is not more than one winter old is known as first-year ice. Sea ice that survives one or more summers is known as multiyear ice. Most Antarctic sea ice is first-year pack ice. Multiyear ice is common in the Arctic, where most of it occurs as pack ice in the Arctic Ocean. Pack ice is made up of many individual pieces of ice known as cakes, if they are less than 20 metres (about 66 feet) across, and floes, which vary from small (20-100 metres about 66-330 feet across) to giant...

C

Cakes, sea ice, 173, 175 Cenozoic era, 183, 214 chatter marks, 125 cirque glaciers, 84, 95, 128-128, 195 cirques, 127-129, 130 Columbia Glacier, 90 congelation ice, 173-175 continental glaciers, 21, 89, 118 of the Arctic, 183-186 depositional landforms of, 137-138 erosional landforms of, 131-135 Cordilleras, 126 Coriolis force, 157, 158, 162 crater glaciers, 84 creep, 26, 119, 144 crevasses, 87-88, 91, 119, 127, 148 cryoconite, 104

The Seasonal Cycle

In most regions where ice occurs, the formation is seasonal in nature. An initial ice cover forms some time after the average daily air temperature falls below the freezing point. The ice cover thickens through the winter period and melts and decays as temperatures warm in the spring. During the formation and thickening periods, energy flows out of the ice cover, and, during the decay period, energy flows into the ice cover. This flow of energy consists of two basic modes of energy exchange the...

The Study Of Permafrost

Although the existence of permafrost had been known to the inhabitants of Siberia for centuries, scientists of the Western world did not take seriously the isolated reports of a great thickness of frozen ground existing under northern forest and grasslands until 1836. Then the Russian naturalist Alexander Theodor von Middendorff measured temperatures to depths of approximately 100 metres (330 feet) of permafrost in the Shargin shaft, an unsuccessful well dug for the governor of the...

Sea

Most sea ice occurs as pack ice, which is very mobile, drifting across the ocean surface under the influence of the wind and ocean currents and moving vertically under the influence of tides, waves, and swells. There is also landfast ice, or fast ice, which is immobile, since it is either attached directly to the coast or seafloor or locked in place between grounded icebergs. Fast ice grows in place by freezing of seawater or by pack ice becoming attached to the shore, seafloor, or icebergs....

Ice Wedges

The most conspicuous and controversial type of ground ice in permafrost is that formed in large ice wedges or masses with parallel or subparallel foliation structures. Most foliated ice masses occur as wedge-shaped, vertical, or inclined sheets or dikes 0.025 to 3 metres (0.1 to 10 feet) wide and 0.3 to 9 metres (1 to 30 feet) high when viewed in transverse cross section. Some masses seen on the face of frozen cliffs may appear as horizontal bodies a few centimetres to 3 metres (10 feet) in...

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In lakes and rivers, 53-73 mechanical properties, 25-26 optical properties, 27 power of on Earth, 225 strength of, 26 thermal properties, 26 ice ages, 28, 75, 76, 116, 183184, 188 ice aprons, 84 icebergs, 21, 78, 95, 96, 101, 104, 105, 106, 109, 115, 145-170, 218 calving of 78, 79, 9 96,1 104, 105, 106, 109, 115, 145, 146-147, 153-154, 209 climatic impacts of, 165-167 danger to ships, 158, 161, 162, 168-170 detection, tracking, and management of, 162, 168-170 distribution of, 158-162 drift...

Glaciers And Sea Level

Sea level is currently rising at about 1.8 mm (0.07 inch) per year. Between 0.3 and 0.7 mm (0.01 to 0.03 inch) per year has been attributed to thermal expansion of ocean water, and most of the remainder is thought to be caused by the melting of glaciers and ice sheets on land. There is concern that the rate in sea-level rise may increase markedly in the future owing to global warming. Unfortunately, the state of the mass balance of the ice on the Earth is poorly known, so the exact...

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Scott, Robert F., 109, 227 sea ice, 145, 170-181 drift of, 176-177 ecological interactions and, 172 first-year ice, 172-173, 177 formation and features of, 172-176 179-181 interactions with oceans, atmosphere, and climate, 177-179 multiyear ice, 172-173, 177, 207 salinity of, 171-172 thickness of, 177 types of, 170 sea level, rise in, 114-115 effect of icebergs on, 165-166 segregated (Taber) ice, 38-39 seracs, 88, 91 Seward-Malaspina glacier, 89 Shackleton, Ernest Henry 227, 229 Shackleton Ice...

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Fast ice, 170, 175 felsenmeer, 143-144, 191 Filchner, Wihelm, 227 Filchner-Ronne Ice Shelf, 98, fjords, 134, 145, 148, 160, 163, 185 floes I75, 176, 179 flow constitutive law of ice, 81, 107-108 flutes, 136, 137, 138 foliated (wedge) ice, 38, 39 foliation of glaciers, 87 frazil ice, 64-65, 67, 173, 175 frost action, 49-50 frost heaving, 50, 51, 52, 143, 190 frost shattering, 143 frost wedging, I47

Antarctica

Filchner Ronne Ice Shelf Antarctica

Fifth in size among the world's continents, Antarctica's landmass is almost wholly covered by a vast ice sheet. It lies almost concentrically around the South Pole. Antarctica the name of which means opposite to the Arctic is the southernmost continent, a circumstance that has had momentous consequences for all aspects of its character. Antarctica covers about 14.2 million square km (5.5 million square miles), and would be essentially circular except for the outflaring Antarctic Peninsula,...

Mountain Glaciers And Other Smaller Ice Masses

In this discussion, the term mountain glaciers includes all perennial ice masses other than the Antarctic and Greenland ice sheets. These ice masses are not necessarily associated with mountains. Sometimes the term small glaciers is used, but only in a relative sense a glacier 10,000 square km (4,000 square miles) in surface area would not be called small in many parts of the world. Mountain glaciers are generally confined to a more or less marked path directing their movement. The shape of the...

The Tce Crystal

At standard atmospheric pressure and at temperatures near 0 C (32T), the ice crystal commonly takes the form of sheets or planes of oxygen atoms joined in a series of open hexagonal rings. The axis parallel to the hexagonal rings is termed the c-axis and coincides with the optical axis of the crystal structure. When viewed perpendicular to the c-axis, the planes appear slightly dimpled. The planes are stacked in a laminar structure that occasionally deforms by gliding, like a deck of cards....

The Arctic

The Arctic is the northernmost region of the Earth, centred on the North Pole and characterized by distinctively polar conditions of climate, plant and animal life, and other physical features. The term is derived from the Greek arktos (bear), referring to the northern constellation of the Bear. It has sometimes been used to designate the area within the Arctic Circle a mathematical line that is drawn at latitude 66 30' N, marking the southern limit of the zone in which there is at least one...

Deep Cores

Most of the Antarctic and Greenland ice sheets are below freezing throughout. Continuous cores, taken in some cases to the bedrock below, allow the sampling of an ice sheet through its entire history of accumulation. Records obtained from these cores represent exciting new developments in paleoclimatology and paleoenvironmental studies. Because there is no melting, the layered structure of the ice preserves a continuous record of snow accumulation and chemistry, air temperature and chemistry,...

Erosional Landforms

A number of landforms result from the movement of glaciers across Earth's surface. Such features in present-day glaciers range from rock polish and glacial grooves on smaller scales to hanging valleys and drumlins on larger ones. Most recently during the Pleistocene Epoch (about 2.6 million to 11,700 years ago), vast continental ice sheets reached into the middle latitudes. Most scientists maintain that these ice sheets carved out many of the world's present-day freshwater basins. Small-Scale...

Rtver Tce Modification

Priit Vesilind

There are a variety of means of modifying ice in rivers. Icebreaking vessels are used to clear paths for other vessels and occasionally to assist in relieving jams on large rivers. Icebreakers are used extensively in northern Europe and to some extent on the Great Lakes and St. Lawrence River of North America. Dusting the ice cover with a dark material such as coal dust or sand can increase the absorption of solar radiation and thus create areas of weakness that aid in an orderly breakup....

The OrigiN of Arctic Icebergs

Graphs About Icebergs

Most Arctic icebergs originate from the fast-flowing glaciers that descend from the Greenland Ice Sheet. Many glaciers are funneled through gaps in the chain of coastal mountains. The irregularity of the bedrock and valley wall topography both slows and accelerates the progress of glaciers. These stresses cause crevasses to form, which are then incorporated into the structure of the icebergs. Arctic bergs tend to be smaller and more randomly shaped than Antarctic bergs and also contain inherent...

The Arctic Ocean

Smallest of the world's oceans, centring approximately on the North Pole, the Arctic Ocean and its marginal seas (the Chukchi, East Siberian, Laptev, Kara, Barents, White, Greenland, and Beaufort some oceanographers also include the Bering and Norwegian seas) are the least-known basins and bodies of water in the world ocean. This lack of knowledge about them results from their remoteness, hostile weather, and perennial or seasonal ice cover. This is changing, however, because the Arctic may...

General Considerations

In order to gain a solid understanding of the different landforms produced by glaciers and their meltwater, it is helpful to discuss the glacial environment and the processes responsible for the formation of such structures. There are numerous types of glaciers, but it is sufficient here to focus on Eskers, narrow ridges of gravel and sand left by a retreating glacier, wind through western Nunavut, Canada, near the Thelon River. Richard Alexander Cooke III two broad classes mountain, or valley,...

Ice Formation In Rivers

The formation of ice in rivers is more complex than in lakes, largely because of the effects of water velocity and turbulence. As in lakes, the surface temperature drops in response to cooling by the air above. Unlike lakes, however, the turbulent mixing in rivers causes the entire water depth to cool uniformly even after its temperature has fallen below the temperature of maximum density (4 C, or 39 F). The general pattern is one in which the water temperature fairly closely follows the...

Depostttonal Landforms

The movement of glaciers across terrestrial environments disturbs the underlying layers of soil and rock, eventually delivering and depositing the collected material to the end, or margin, of the glacier. As a glacier moves along a valley, it picks up rock debris from the valley walls and floor, transporting it in, on, or under the ice. This scouring process also occurs in continental glaciers. When the material reaches the lower parts of the glacier where ablation is dominant, it is...

Decay And Ice Jams

In late winter, as air temperatures rise above the freezing point, river ice begins to melt owing to heat transfer from above and to the action of the slightly warm water flowing beneath. As occurs in lake ice, river ice also may deteriorate and rot because of absorption of solar radiation. On the undersurface, the action of the turbulent flowing water causes a melt pattern in the form of a wavy relief, with the waves oriented crosswise to the current direction. Eventually, if the ice cover is...

Iceberg Scour and SeDiMeNT Transport

When an iceberg runs aground, it can plow a furrow several metres deep in the seabed that may extend for tens of kilometres. Iceberg scour marks have been known from the Labrador Sea and Grand Banks since the early i970s. In the Arctic, many marks are found at depths of more than 400 metres (1,300 feet), whereas the deepest known sill, or submerged ridge, within Greenland fjords is 220 metres (about 725 feet) deep. This unsolved anomaly suggests that icebergs were much deeper in the past or...

Ice Formation Tn Lakes

Cool Down With Water And Ice Pics

The setting for the development of ice cover in lakes is the annual evolution of the temperature structure of lake water. In most lakes during the summer, a layer of warm water of lower density lies above colder water below. In late summer, as air temperatures fall, this top layer begins to cool. After it has cooled and has reached the same density as the water below, the water column becomes isothermal (i.e., there is a uniform temperature at all depths). With further cooling, the top water...

Active Wedges Inactive Wedges And Icewedge Casts

Ice wedges may be classified as active, inactive, and ice-wedge casts. Active ice wedges are those that are actively growing. The wedge may not crack every year, but during many or most years cracking does occur, and an increment of ice is added. Ice wedges require a much more rigorous climate to grow than does permafrost. The permafrost table must be chilled to -15 to -20 C (5 to -4 F) for contraction cracks to form. On the average, it is assumed that ice wedges generally grow in a climate...