Meltwater
Meltwater (or melt water) is water released by the
When meltwater pools on the surface rather than flowing, it forms
Water source
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Meltwater is water that melts off of glaciers or snow. It then flows into a river or collects on the surface forming a melt pond, which may re-freeze. It may also collect under ice or frozen ground.
Meltwater provides drinking water for a large proportion of the world's population, as well as providing water for irrigation 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[1] and the shrinking volume of glaciers.[2]
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. After that, leftover water will flow into oceans causing sea levels to rise. Snow melt hundreds of miles away can contribute to river replenishment.
In North America, 78% of meltwater flows west of the Continental Divide, and 22% flows east of the Continental Divide.[5] Agriculture in Wyoming and Alberta relies on water sources made more stable during the growing season by glacial meltwater.[2]
The Tian Shan 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.[2]
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.[6] Cities that rely heavily on glacial meltwater include La Paz and El Alto in Bolivia, about 30%.[6][2] 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.[6] 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.[7]
Glacial meltwater
Glacial meltwater comes from glacial melt due to external forces or by
giving a milky turquoise appearance.Meltwater also acts as a lubricant in the basal sliding of glaciers. GPS measurements of ice flow have revealed that glacial movement is greatest in summer when the meltwater levels are highest.[9]
Glacial meltwater can also affect important fisheries, such as in Kenai River, Alaska.[2]
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 where rapid vertical motion of the ice sheet surface has suggested shifting of a subglacial water body.[10]
It can also destabilize glacial lakes leading to sudden floods, and destabilize snowpack causing avalanches.[11] 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.
Global warming
In a report published in June 2007, the
The snow of glaciers in the central Andes melted rapidly due to a heatwave,[14] increasing the proportion of darker-coloured mountains. With alpine glacier volume in decline, much of the environment is affected.
These black particles are recognized for their propensity to change the albedo – or reflectance – of a glacier. Pollution particles affect albedo by preventing sun energy from bouncing off a glacier's white, gleaming surface and instead absorbing the heat, causing the glacier to melt.
See also
- Extreme Ice Survey
- Groundwater
- Kryal
- Moulin (geology)
- Snowmelt
- Surface water
- False bottom (sea ice)
In the media
- June 4, 2007, BBC: UN warning over global ice loss
References
- S2CID 216031932.
- ^ PMID 28874558.
- ^ a b "Snowfall giving Lake Mead a lift". Las Vegas Review-Journal. 2011-08-07. Retrieved 2021-05-30.
- ^ "Melting snow and groundwater levels in Sierra Nevadas". ScienceDaily. Retrieved 2021-05-30.
- S2CID 210271648.
- ^ a b c "Glacier melt and water security". Imperial College London. Retrieved 2021-05-30.
- ISSN 2214-5818.
- ISSN 1944-7973.
- ^ Garner, Rob (2013-07-22). "'Like Butter': Study Explains Surprising Acceleration of Greenland's Inland Ice". NASA. Archived from the original on 2013-09-27. Retrieved 2016-05-12.
- ISSN 0091-7613.
- ^ a b "Melting Ice—A Hot Topic? New UNEP Report Shows Just How Hot It's Getting". United Nations Environment Programme (UNEP). 2007-06-04. Archived from the original on 2009-07-07. Retrieved 2016-05-12.
- .
- doi:10.1130/g20170.1.
- ^ "Losing a Layer of Protection". NASA Earth Observatory. June 14, 2022. p. 1. Retrieved June 14, 2022.