Glaciers Sea Ice

Wilkins Ice Shelf

Merorites Hurling Towards Glaciers

The Wilkins Ice Shelf is a large body of floating ice covering the greater part of Wilkins Sound off the western coast of the Antarctic Peninsula. Both the ice shelf and the sound were named for Australian-born British explorer Sir George Hubert Wilkins, who first scouted the region by airplane in late December 1928. The Wilkins Ice Shelf spanned the region between Alexander Island, Charcot Island, and Latady Island in the Bellingshausen Sea, an area of about 16,000 square km (6,200 square...

General Considerations

Types Materails For Parks

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,...

The Local Thickness Of Permafrost

Vegetation Destroyed Snow

The thickness and areal distribution of permafrost are directly affected by snow and vegetation cover, topography, bodies of water, the interior heat of the Earth, and the temperature of the atmosphere. The most conspicuous change in thickness of permafrost is related to climate. At Barrow, Alaska, the mean annual air temperature is -12 C (10T), and the thickness is 400 metres (about 1,300 feet). At Fairbanks, Alaska, in the discontinuous zone of permafrost in central Alaska, the mean annual...

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...

Ice Formation In Rivers

Frazil Ice Tends Generated

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...

Erosional Landforms

Ice Landfarms Images

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...

Problems Posed By Permafrost

When Was The Alaskan Pipeline Built

Permafrost poses unique challenges to those who wish to develop Earth's polar regions. Thawing, subsidence, frost action, and freezing can wreak havoc on infrastructure and permanent constructions that disturb the frozen ground. To maintain the stability of the ground (thus reducing the maintenance costs of buildings and roads), construction activities must take these phenomena into account before buildings are erected and transportation lines are laid out. Often, buildings, pipes, and...

Mountain Glaciers And Other Smaller Ice Masses

Variety Outlet Glaciers

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 OrigiN of Arctic Icebergs

Iceberg Type

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...

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...

The Great Tce Sheets

Two great ice masses, the Antarctic and Greenland ice sheets, stand out in the world today and may be similar in many respects to the large Pleistocene ice sheets. About 99 percent of the world's glacier ice is in these two ice masses 91 percent in Antarctica alone. The bedrock of the continent of Antarctica is almost completely buried under ice. Mountain ranges and isolated nunataks (a term derived from Greenland's Inuit language, used for individual mountains surrounded by ice) locally...

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...

Accumulation And Ablation Of The Ice Sheets

The size and thickness of an ice sheet depends on the amount of precipitation it receives and the amount of material it loses to melting, calving, and other processes. An ice sheet grows in years where accumulation exceeds ablation and declines in years where ablation exceeds accumulation. The rate of precipitation on the Antarctic Ice Sheet is so low that it may be called a cold desert. Snow accumulation over much of the vast polar plateau is less than five cm (two inches) water equivalent per...

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...

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...

Rock Glacier

A rock glacier is a tonguelike body of coarse rock fragments, found in high mountains above the timberline, that moves slowly down a valley. The rock material usually has fallen from the valley walls and may contain large boulders it resembles the material left at the terminus of a true glacier. Interstitial ice usually occurs in the centre of rock glaciers. Where the ice approaches the terminus, it melts and releases the rock material, which then forms a steep talus slope. A rock glacier may...

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...

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 Formation And Characteristics Of Glacier

Glacier ice is an aggregate of irregularly shaped, interlocking single crystals that range in size from a few millimetres to several tens of centimetres. Many processes are involved in the transformation of snowpacks to glacier ice, and they proceed at a rate that depends on wetness and temperature. Snow crystals in the atmosphere are tiny hexagonal plates, needles, stars, or other intricate shapes. In a deposited snowpack these intricate shapes are usually unstable, and molecules tend to...

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...

Sea Ice Formation and Features

When Did Glaciers First Appear

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...

The Power Of

Even though ice covers only about 10 percent of Earth's surface, it is a significant material with a great deal of influence over life on Earth. The majority of this ice is found at or near the poles, both on top of and within the upper layers of soil and rock. During the winter, many temperate-zone lakes and rivers freeze, thawing when air temperatures rise in the spring. Ice forms from liquid water, fractures, melts, and decays. The movement of glacial ice over the land scours the soil from...

The Geographic Distribution Of Lake

The first appearance of lake ice follows by about one month the date at which the long-term average daily air temperature first falls below freezing. Ice appears first in smaller shallow lakes, often forming and melting several times in response to the diurnal variations in air temperature, and finally forms completely as air temperatures remain below the freezing point. Larger lakes freeze over somewhat later because of the longer time required to cool the water. In North America the...

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....

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...

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...

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....