Meltwater
Encyclopedia
Melting
Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...
of snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
or 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...
, including glacial ice and ice shelf
Ice shelf
An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland and Canada. The boundary between the floating ice shelf and the grounded ice that feeds it is called...
s over oceans. Meltwater is often found in the ablation zone
Ablation zone
Ablation zone refers to the low altitude area of a glacier or ice sheet where there is a net loss in ice mass due to melting, sublimation, evaporation, or calving. The ablation zone is delineated by the equilibrium line altitude , or snow line, which separates the ablation zone and the high...
of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during volcanic eruptions
Volcanic Eruptions
Volcanic Eruptions is a company owned by Crispin Glover. The company produces and issues Glover's work: It has released two films to date, What Is It? and its sequel, It is Fine! EVERYTHING IS FINE . Its current plans include releasing the final film in the trilogy titled It Is Mine...
, in a similar way in which the more dangerous lahar
Lahar
A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. The term is a shortened version of "berlahar" which originated in the Javanese language of...
s form.
When meltwater pools on the surface rather than flowing, it forms melt ponds. As the weather gets colder meltwater will often re-freeze. Meltwater can collect or melt under the ice's surface. These pools of water, known as subglacial lake
Subglacial lake
A subglacial lake is a lake under a glacier, typically an ice cap or ice sheet. There are many such lakes, with Lake Vostok in Antarctica being by far the largest known at present.-Characteristics:...
s can form due to geothermal heat and friction.
Water source
Meltwater provides drinking waterDrinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
for a large proportion of the world's population, as well as providing water for irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
and hydroelectric plants
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
. Some cities around the world have large lakes that collect snow melt to supplement water supply. Cities that source water from meltwater include Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
, Canberra
Canberra
Canberra is the capital city of Australia. With a population of over 345,000, it is Australia's largest inland city and the eighth-largest city overall. The city is located at the northern end of the Australian Capital Territory , south-west of Sydney, and north-east of Melbourne...
, Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
, Las Vegas
Las Vegas, Nevada
Las Vegas is the most populous city in the U.S. state of Nevada and is also the county seat of Clark County, Nevada. Las Vegas is an internationally renowned major resort city for gambling, shopping, and fine dining. The city bills itself as The Entertainment Capital of the World, and is famous...
amongst others.
Glacial meltwater
Rock flour
Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size...
", sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
that has been transported through the rivers to the lakes. This sediment comes from rocks grinding together underneath the glacier. The fine powder
Powder (substance)
A powder is a dry,thick bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material...
is then suspended in the water and refracts sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
therefor giving the milky turquoise appearance.
Meltwater also acts as a lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
in the basal sliding
Basal sliding
Basal sliding is the act of a glacier sliding over the bed before it due to meltwater under the ice acting as a lubricant. This movement very much depends on the temperature of the area, the slope of the glacier, the bed's sediment size, the amount of meltwater from the glacier, and the glacier's...
of glaciers. Using GPS measurements to study ice flow has revealed that glacial movement
Glacial motion
Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers...
is greatest in summer when the meltwater levels are highest.
Rapid changes
Meltwater can be an indication of abrupt climate changeAbrupt climate change
An abrupt climate change occurs when the climate system is forced to transition to a new state at a rate that is determined by the climate system itself, and which is more rapid than the rate of change of the external forcing...
. An instance of a large meltwater body is the case of the region of a tributary of Bindschadler Ice Stream, West Antarctica
West Antarctica
West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of the continent that lies within the Western Hemisphere including the Antarctic Peninsula.-Location and description:...
where rapid vertical motion of the ice sheet surface has suggested shifting of a subglacial water body.
It can also destabilize glacial lakes leading to sudden flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
s, and destabilize snowpack causing avalanche
Avalanche
An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...
s. Dammed glacial meltwater from a moraine-dammed lake that is released suddenly can resulted in the floods that created the granite chasms in Purgatory Chasm State Reservation
Purgatory Chasm State Reservation
Purgatory Chasm State Reservation is a state park in Sutton, Massachusetts. The park, managed by the Massachusetts Department of Conservation and Recreation, is notable for its long, deep chasm of granite bedrock featuring abrupt precipices and boulder caves in which ice lingers into the early...
.
Global warming
In a report published in June 2007, the United Nations Environment ProgrammeUnited Nations Environment Programme
The United Nations Environment Programme coordinates United Nations environmental activities, assisting developing countries in implementing environmentally sound policies and practices. It was founded as a result of the United Nations Conference on the Human Environment in June 1972 and has its...
estimated that global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
could lead to 40% of the world population
World population
The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be billion by the United States Census Bureau...
being affected by the loss of glaciers, snow and the associated meltwater in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. Historically Meltwater pulse 1A
Meltwater pulse 1A
Meltwater pulse 1A was an instance in the sea level rise of about 20 m in less than 500 years, perhaps just 200 years. The meltwater event occurred in a period of rapid climate change when the Holocene glacial retreat was going on during the end of the last ice age...
was a prominent feature of the last deglaciation and took place 14.7-14.2 thousand years ago.
See also
- Extreme Ice SurveyExtreme Ice SurveyThe Extreme Ice Survey documents rapid changes on glaciers across the Northern Hemisphere. It is the most wide-ranging glacier study ever conducted using ground-based, real-time photography. The Extreme Ice Survey uses time-lapse photography, conventional photography and video to illustrate the...
- GroundwaterGroundwaterGroundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
- Moulin (geology)Moulin (geology)A moulin or glacier mill is a roughly circular, vertical to nearly vertical well-like shaft within the a glacier through which water enters it from the surface. The term is derived from the French word for mill....
- SnowmeltSnowmeltIn hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many parts of the world, in some cases contributing high...
- Surface waterSurface waterSurface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....
In the media
- June 4, 2007, BBCBBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
: UN warning over global ice loss