Kinney Run looking downstream in Spring 2015

Cavell Glacier with Crevices and Annual Rings

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 inc ...

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 ...

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 opaqu ...

, 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 over many years, often centuries. It acquires distinguishing features, such as ...

, tabular icebergs and

ice shelves An ice shelf is a large 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, Northern Canada, and the Russian Arctic. The b ...

over oceans. Meltwater is often found in the

ablation zone Ablation zone or ''ablation area'' refers to the low-altitude area of a glacier or ice sheet below firn with a net loss in ice mass due to melting, sublimation, evaporation, ice calving, aeolian processes like blowing snow, avalanche, and any ...

of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during

volcanic eruptions Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

, in a similar way in which the more dangerous lahars form. When meltwater pools on the surface rather than flowing, it forms

melt pond Melt ponds are pools of open water that form on sea ice in the warmer months of spring and summer. The ponds are also found on glacial ice and ice shelves. Ponds of melted water can also develop under the ice. Melt ponds are usually darker th ...

s. 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 A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point ...

s 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 crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...

and hydroelectric plants. 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,

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...

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, 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 Water security is the focused goal of water policy and water management. A society with a high level of water security makes the most of water's benefits for humans and ecosystems and limits the risk of destructive impacts associated with water. T ...

year-round, but this is threatened by climate change and

aridification Aridification is the process of a region becoming increasingly arid, or dry. It refers to long term change, rather than seasonal variation. It is often measured as the reduction of average soil moisture content. It can be caused by reduced precip ...

. Cities that rely heavily on glacial meltwater include La Paz and

El Alto El Alto (Spanish for "The Heights") is the second-largest city in Bolivia, located adjacent to La Paz in Pedro Domingo Murillo Province on the Altiplano highlands. El Alto is today one of Bolivia's fastest-growing urban centers, with an estimat ...

in Bolivia, 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

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 of ...

. 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, sa ...

that has been transported through the rivers to the lakes. This sediment comes from rocks grinding together underneath the glacier. The fine

powder A powder is a dry, bulk solid composed of many 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 distin ...

is then suspended in the water and absorbs and scatters varying colors of sunlight, giving a milky turquoise appearance. Melting glacier (Skaftafellsjökull)

Meltwater also acts as a lubricant 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 The Kenai River called ''Kahtnu'' in the Dena'ina language, is the longest river in the Kenai Peninsula of southcentral Alaska. It runs westward from Kenai Lake in the Kenai Mountains, through the Kenai National Wildlife Refuge and Skilak Lak ...

, Alaska.

Rapid changes

Meltwater can be an indication of

abrupt climate change An abrupt climate change occurs when the climate system is forced to transition at a rate that is determined by the climate system energy-balance, and which is more rapid than the rate of change of the external forcing, though it may include sud ...

. An instance of a large meltwater body is the case of the region of a tributary of Bindschadler Ice Stream, West Antarctica 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 eart ...

s. Dammed glacial meltwater from a

moraine-dammed lake A moraine-dammed lake occurs when the terminal moraine has prevented some meltwater from leaving the valley. Its most common shape is that of a long ribbon (ribbon lake). Example of moraine dammed lakes include: *Argentina/Chile: General Carre ...

that is released suddenly can result in the floods, such as those that created the granite chasms in Purgatory Chasm State Reservation.

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 th ...

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 corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...

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! 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 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 that refl ...

– or

reflectance The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...

– 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 over many years, often centuries. It acquires distinguishing features, such as ...

. Pollution particles affect albedo by preventing

sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

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 ...

, causing the glacier to melt.

Water source

Glacial meltwater

Rapid changes

Global warming

See also

In the media

References

External links