Glacier

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Glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. Columbia Icefields, Alberta Canada
Glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. Columbia Icefields, Alberta Canada
Columbia Icefields, Alberta Canada
Columbia Icefields, Alberta Canada
Cross section of an alpine glacier showing snow being converted into glacier ice (the left side of the figure) and the two major zones of a glacier’s surface. The red arrows show the direction and relative speed of different parts of the glacier. The longer the arrow, the faster ice is moving.
Cross section of an alpine glacier showing snow being converted into glacier ice (the left side of the figure) and the two major zones of a glacier’s surface. The red arrows show the direction and relative speed of different parts of the glacier. The longer the arrow, the faster ice is moving.

Glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years.

The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology.

Glacier ice is the largest reservoir of fresh water on Earth, and is second only to oceans as the largest reservoir of total water. Glaciers cover vast areas of the polar regions and are found in mountain ranges of every continent including Australasia (there are glaciers in New Zealand).

In the tropics glaciers are restricted to the highest mountains. The processes and 'landforms' caused by glaciers and related to them are referred to as glacial. The process of glacier growth and establishment is called glaciation.

Glaciers are indicators of climate and are important to world water resources and sea level variation. They are an important component of the more encompassing cryosphere.

As new snow accumulates, it buries and compresses the old snow. Under the weight of the overlying snow, the old snow is transformed from a fluffy mass of ice crystals into dense, hard ice.

This process occurs on the upper part of a glacier, at higher altitudes, where more snow accumulates than is lost each year. This is called the “accumulation zone”, and is typically covered with snow year-round.

The glacier is in constant motion, and the ice in the accumulation zone flows down to lower altitudes, which is called the “ablation zone”. The ablation zone is located in the lower part of the the glacier where more snow is lost than accumulates. In late summer, when the seasonal snow has melted, the bare ice of the ablation zone is exposed.

Glaciers reached their Holocene (the past 10 000 years) maximum extent towards the end of the Little Ice Age (the Little Ice Age extended from the early 14th to mid-19th century.) Since then, glaciers around the globe have been shrinking dramatically, with increasing rates of ice loss since the mid-1980s. On a time-scale of decades, glaciers in various mountain ranges have shown intermittent readvances. However, under the present climate scenarios, the ongoing trend of worldwide and fast, if not accelerating, glacier shrinkage on the century time-scale is not a periodic change and may lead to the deglaciation of many mountain regions by the end of the 21st century.

Glacial retreat and melting of permafrost will shift cryospheric hazard zones.

This, in combination with the increasing socio-economic development in mountain regions, will most probably lead to hazard conditions beyond historical precedence. Changes in glaciers may strongly affect the seasonal availability of freshwater, especially when the reduction of glacier runoff occurs in combination with reduced snow cover in winter and earlier snowmelt, less summer precipitation, and enhanced evaporation due to warmer temperatures. The most critical regions will be those where large populations depend mainly on water resources from glaciers during the dry season and glaciated mountain ranges that are densely populated and highly developed.

[edit] Glaciers and ice caps

Glaciers and ice caps (lowest and [highest] estimates):

  • Area Covered (million square km)0.51 [0.54]
  • Ice Volume (million cubic km)0.05 [0.13]
  • Potential Sea Level Rise (cm)15 [37]

Source: IPCC 2007

[edit] Also See

[edit] Reference:

  • Wikipedia see Glacier [1]
  • Rocky Mountain National Park Glacier Basics [2]
  • Glaciers and Ice Caps [3]

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