![Cavell Glacier with Crevices and Annual Rings](https://upload.wikimedia.org/wikipedia/commons/7/75/Cavell_Glacier_with_Crevices_and_Annual_Rings.jpg)
Meltwater is water released by the
melting
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which incre ...
of
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
or
ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...
, including
glacial ice
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
, tabular
iceberg
An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...
s and
ice shelves over oceans. Meltwater is often found in the
ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during
volcanic eruptions, in a similar way in which the more dangerous
lahar
A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent 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.
Lahars are extreme ...
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 lakes can form due to geothermal heat and friction.
Water source
Meltwater provides
drinking water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
for a large proportion of the world's population, as well as providing water for
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
and
hydroelectric plants
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...
. This meltwater can originate from seasonal snowfall, or from the melting of more permanent glaciers. Climate change threatens the precipitation of snow and the shrinking volume of glaciers.
Some cities around the world have large lakes that collect snow melt to supplement water supply. Others have artificial reservoirs that collect water from rivers, which receive large influxes of meltwater from their higher elevation tributaries. Snow melt hundreds of miles away can contribute to river replenishment.
Snowfall can also replenish groundwater in a highly variable process. Cities that indirectly source water from meltwater include
Melbourne
Melbourne ( ; Boonwurrung/Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a met ...
,
Canberra
Canberra ( )
is the capital city of Australia. Founded following the federation of the colonies of Australia as the seat of government for the new nation, it is Australia's largest inland city and the eighth-largest city overall. The ci ...
,
Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
,
Las Vegas
Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Vegas ...
among others.
In North America, 78% of meltwater flows west of the
Continental Divide
A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...
, and 22% flows east of the Continental Divide. Agriculture in Wyoming and Alberta relies on water sources made more stable during the growing season by glacial meltwater.
The
Tian Shan
The Tian Shan,, , otk, 𐰴𐰣 𐱅𐰭𐰼𐰃, , tr, Tanrı Dağı, mn, Тэнгэр уул, , ug, تەڭرىتاغ, , , kk, Тәңіртауы / Алатау, , , ky, Теңир-Тоо / Ала-Тоо, , , uz, Tyan-Shan / Tangritog‘ ...
region in China once had such significant glacial runoff that it was known as the "Green Labyrinth", but it has faced significant reduction in glacier volume from 1964 to 2004 and become more arid, already impacting the sustainability of water sources.
In tropical regions, there is much seasonal variability in the flow of mountainous rivers, and glacial meltwater provides a buffer for this variability providing more
water security year-round, but this is threatened by climate change and
aridification.
Cities that rely heavily on glacial meltwater include
La Paz
La Paz (), officially known as Nuestra Señora de La Paz (Spanish pronunciation: ), is the seat of government of the Bolivia, Plurinational State of Bolivia. With an estimated 816,044 residents as of 2020, La Paz is the List of Bolivian cities ...
and
El Alto in
Bolivia
, image_flag = Bandera de Bolivia (Estado).svg
, flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center
, flag_alt2 = 7 × 7 square p ...
, about 30%.
Changes in the glacial meltwater are a concern in more remote highland regions of the Andes, where the proportion of water from glacial melt is much greater than in lower elevations.
In parts of the Bolivian Andes, surface water contributions from glaciers are as high as 31-65% in the wet season and 39-71% in the dry season.
Glacial meltwater
![Fryxellsee Opt](https://upload.wikimedia.org/wikipedia/commons/8/8f/Fryxellsee_Opt.jpg)
Glacial meltwater comes from glacial melt due to external forces or by
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
and
geothermal heat
Geothermal heating is the direct use of geothermal energy for some heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ o ...
. Often, there will be rivers flowing through glaciers into lakes. These brilliantly blue lakes get their color from "
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. Because the material is very small, it becomes suspe ...
",
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
that has been transported through the rivers to the lakes. This sediment comes from rocks grinding together underneath the glacier. The fine
powder is then suspended in the water and absorbs and scatters varying colors of
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
, giving a milky turquoise appearance.
![Melting glacier (Skaftafellsjökull)](https://upload.wikimedia.org/wikipedia/commons/9/9d/Melting_glacier_%28Skaftafellsj%C3%B6kull%29.jpg)
Meltwater also acts as a
lubricant
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
in the
basal sliding
Basal sliding is the act of a glacier sliding over the bed 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 roughness, the amount of meltwater f ...
of glaciers. GPS measurements of ice flow have revealed that
glacial movement is greatest in summer when the meltwater levels are highest.
Glacial meltwater can also affect important fisheries, such as in
Kenai River, Alaska.
Rapid changes
Meltwater can be an indication of
abrupt climate change. An instance of a large meltwater body is the case of the region of a tributary of Bindschadler Ice Stream,
West Antarctica
West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of that continent that lies within the Western Hemisphere, and includes the Antarctic Peninsula. It is separated from East Antarctica by the Transant ...
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
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
s, and destabilize
snowpack
Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as th ...
causing
avalanche
An avalanche is a rapid flow of snow down a slope, such as a hill or mountain.
Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earth ...
s.
Dammed glacial meltwater from a
moraine-dammed lake that is released suddenly can result in the floods, such as those that created the granite chasms in
Purgatory Chasm State Reservation
Purgatory Chasm State Reservation is a protected area, protected state park in Sutton, Massachusetts, Sutton, Massachusetts. Located within Blackstone Valley, the reservation is managed by the Massachusetts Department of Conservation and Recrea ...
.
Global warming
In a report published in June 2007, the
United Nations Environment Programme
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on th ...
estimated that
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
could lead to 40% of the
world population
In demographics, the world population is the total number of humans currently living. It was estimated by the United Nations to have exceeded 8 billion in November 2022. It took over 200,000 years of human prehistory and history for the ...
being affected by the loss of glaciers, snow and the associated meltwater in Asia.
The predicted trend of glacial melt signifies seasonal climate extremes in these regions of Asia. Historically
Meltwater pulse 1A
Meltwater pulse 1A (MWP1a) is the name used by Quaternary geologists, paleoclimatologists, and oceanographers for a period of rapid post-glacial sea level rise, between 13,500 and 14,700 calendar years ago, during which global sea level rose betw ...
was a prominent feature of the last deglaciation and took place 14.7-14.2 thousand years ago.
According to
Google
Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...
most searched question is
pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
to blame for the
melting of glaciers
The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and, in the longer term, the level of the oceans. Deglaciation occur ...
! and effecting our
environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
These black particles are recognized for their propensity to change the
albedo
Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
– or
reflectance – of a
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
. Pollution particles affect albedo by preventing
sun energy from bouncing off a glacier's white, gleaming surface and instead absorbing the
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
, causing the glacier to
melt
Melt may refer to:
Science and technology
* Melting, in physics, the process of heating a solid substance to a liquid
* Melt (manufacturing), the semi-liquid material used in steelmaking and glassblowing
* Melt (geology), magma
** Melt inclusions, ...
.
See also
*
Extreme Ice Survey
The Extreme Ice Survey (EIS), based in Boulder, Colorado, uses time-lapse photography, conventional photography and video to document the effects of global warming on glacial ice. It is the most wide-ranging glacier study ever conducted using gro ...
*
Groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
*
Kryal
The Kryal is the portion of a stream (usually the upper portion) fed by meltwaters from a glacier, permafrost or permanent ice-fields.
References
Glaciers
{{Topography-stub ...
*
Moulin (geology)
A moulin (or glacier mill) is a roughly circular, vertical (or nearly vertical) well-like shaft formed where a surface meltstream exploits a weakness in the ice. The term is derived from the French word for mill.Neuendorf, K.K.E., J.P. Mehl, Jr. ...
*
Snowmelt
In 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 part ...
*
Surface water
Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean.
The vast majority of surface water is produced by prec ...
In the media
*June 4, 2007, ''
BBC #REDIRECT BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board ex ...
''
UN warning over global ice loss
References
External links
United Nations Environment Program: Global Outlook for Ice and Snow
{{Authority control
Drinking water
Water supply
Glaciology