Glacial stream

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Image shows the different stream types that are found on a glacier. The different streams are supraglacial, subglacial, englacial and proglacial. Different types of Glacier Streams.jpg
Image shows the different stream types that are found on a glacier. The different streams are supraglacial, subglacial, englacial and proglacial.

A glacier stream is a channelized area that is formed by a glacier in which liquid water accumulates and flows. [1] Glacial streams are also commonly referred to as "glacier stream" or/and "glacial meltwater stream". The movement of the water is influenced and directed by gravity and the melting of ice. [1] The melting of ice forms different types of glacial streams such as supraglacial, englacial, subglacial and proglacial streams. [1] Water enters supraglacial streams that sit at the top of the glacier via filtering through snow in the accumulation zone and forming slush pools at the FIRN zone. [2] The water accumulates on top of the glacier in supraglacial lakes and into supraglacial stream channels. [2] The meltwater then flows through various different streams either entering inside the glacier into englacial channels or under the glacier into subglacial channels. [2] Finally, the water leaves the glacier through proglacial streams or lakes. [2] Proglacial streams do not only act as the terminus point but can also receive meltwater. [2] Glacial streams can play a significant role in energy exchange and in the transport of meltwater and sediment. [3]

Contents

Stream/Channel Formation

Glaciers erode and deposit sediment by advancing and retreating. [4] Erosion occurs by abrasion and plucking. [4] These processes are dependent on a variety of factors such as plate tectonic movement, volcanic activity, and changes in atmospheric gas composition. [5] Glacial erosion often causes U-shaped valleys to form. [6] These valleys allow for directed water movement such as seen in glacial streams with meltwater. [6] Subglacial fluvial erosion and glacial outwash occurs from the melting of the glacier and creates water flow that can wear bedrock. [4] Glacial streams can range in width and height from a few centimeters to several tens of meters. [3] The streams can be classified using three metrics: surface, incision, and canyons. [3] The incision and sinuosity is impacted by the discharge and slope. [3] When the discharge and slope is greater, the incision is faster and sinuosity is higher. [3] The sinuosity being higher means the valley between the top of the banks distance is greater. [3] This causes formation of trapezoidal canyon like valleys. [3] The stream slope is influenced by basal topography, ice thickness and flow, and glacier ablation. [3] A real life example of meltwater stream channel formation is shown in this video of the Fox Glacier.

Geographical Distribution

Rupal River is an example of glacial stream. Rupal River - Pakistan.jpg
Rupal River is an example of glacial stream.

Glacial streams are found globally in regions of glacier presence, [3] often located in high latitudes or alpine environments. [7] Remote sensing and other GIS systems are often used to detect and study these streams. [3] [8] The length of glacial streams varies substantially between different regions, often dependent on the size of the watershed it is located in and the characteristics of the glacier that formed the stream channel. [2] [3]

An example of a glacial stream is the Rupal River.

Hydrology of Glacial Meltwater Streams

Glacial stream discharge fluctuates throughout the year depending on snowmelt, glacier ablation, channel boundary melt, and precipitation. [3] Measurements of discharge increase during spring and are highest in the summer, during which warmer temperatures promote the additions of meltwater. [7] Meltwater is a major contributor to many glacial stream’s annual water budget. [7] The amount of meltwater a glacial stream receives is dependent on the size of the watershed it is located in; larger watersheds tend to have greater accumulations of snow, and therefore high measurements of meltwater and annual discharge. [3] However, in regions of prominent glacier presence, glacial streams only receive an average of 52% of meltwater production; a large portion of meltwater runoff enters the crevasses of the surrounding glacier. [3]

Glacial streams often undergo flood pulses during spring and summer due to glacial melting. [9] These flood pulses alter stream discharge in its velocity and momentum, often increasing the glacial stream’s composition of nutrients, solutes, and dissolved gas. [9] Ecosystem productivity often measures highest in glacial streams that fluctuate in their rates of discharge. [9]

Ecology

The harsh condition of glacial streams is not only because glacial streams are often located at high altitude and latitude, but also the consistent contribution of melting snow. [10] Thus, low water temperature, variable discharge rates, unstable substrate and riverbed, and increased turbidity and sediment load are the typical condition of glacial streams. [10]

The growth of invertebrates in glacial streams is faster characterized by higher body mass. [10] The reasons are the low level of competition and the abundant food source due to less organisms surviving. [10] The dominant species is Diamesinae from the chironomid subfamily. [10] Other species able to live in glacial streams include Orthocladiinae, which is the second dominant species in cold streams, benthic algae, periphyton, and the insect family Chironomidae. [10]

In the summer, glacial streams experience high stream flow because of ice melt. [8] The high flow is characterized by high turbidity and sediment transport, which reduces the biomass of the resident periphyton. [8] At the end of summer, ice melt is reduced and stream flow decreases, causing an increase in the periphyton population. [8]

Moreover, in similar latitude and altitude glacial stream, the beta diversity is similar and enhanced compared to non-glacial reaches.

Stream types

Alpine streams can be characterized as kyral, krenal, or rhithral, and vary in ecology. [11]

Kyral

Kyral streams are the upper-most reach of glacial streams, located above the permanent snowline of glaciers. [11] These streams are fed by glacial meltwater and consist of temperatures below 4°C. [11] Low temperatures control the organisms that are found in this stream section. [11] Generally, there are no organisms within the first few meters below the glacial input; organisms increase in their abundance and diversity downstream. [11] Typical species of kyral streams consist of diamesine chironomids and simuliids. [11] These organisms feed upon algae and allochthonous organic matter. No fish, angiosperms or plankton are found in this segment. [11]

Krenal

Krenal streams (also known as springbrooks) can be found at all altitudes and receive their sources from groundwater. [11] This water source provides the stream with a well-oxygenated environment that has constant flow and stable temperatures, varying only 1-2°C during the year. [11] These conditions allow for a diverse community of organisms to inhabit the environment. [11] Various types of algae, moss and tundra vegetation can be found here. [11] Some fish, like the arctic char, rely on these streams for spawning sites in the winter months. [11] At higher elevations, Chironomidae, specifically Diamesa, are the dominant fauna. [11] At lower elevations, amphipods, isopods and molluscs become more dominant. [11]

Rhithral

Rhithral stream sources come from snowmelt, causing soft water that is made up predominantly of sodium ions. [11] The temperature varies widely, ranging from 5-10°C. [11] The vegetation found here are mainly bryophytes, and macroalgae, such as chrysophytes, chlorophytes, cyanophytes and rhodophytes. [11] For invertebrates, Plecoptera, Ephemeroptera, Trichoptera, Diptera, turbellarians, acarines, oligochaetes and nematodes are typically found in these streams. [11] There are a limited number of fish species that inhabit this environment, like salmonids, and sometimes trout, catfish or darters. [11]

Human Impacts

Climate Change

Climate change induced glacial recession may reduce the effect of the seasonal stream flow, as well as impact the stream's sources of water. [8] [12] It is expected that with glacial recession, there will eventually be less surface water flow. [8] This is because high alpine areas generally have almost no below ground water storage, and thus, have an absence of aquifers that could have provided the stream with a reliable alternative water source. [8] This means that glacial streams could become intermittent in the future. [8] Streams that have reliable water sources and do not dry up intermittently, will likely be warmer in temperature, which will allow organisms downstream to move to higher elevations and claim new territory. [8] A study done in southeastern Alaska suggests that glacial recession will influence changes in the physical and chemical properties of coastal waters that are connected downstream from glacial streams. [13] These changes could have serious consequences for salmon spawning, ecosystem productivity, and eutrophication. [13]

Pollution

Alpine areas are generally seen as pristine environments, far away from human influence. [14] However, this is not the case. Airborne contaminants, such as some pesticides, can accumulate in alpine areas and pose health risks to aquatic organisms living in these environments. [14] Contamination by persistent organic pollutants (POPs) mostly occurs from local emissions and transport. [15] Glacial recession of older glacial ice, containing contaminants that were deposited on the ice decades ago (eg. DDT), will enter the stream ecosystem, where it can have health implications for the organisms living in / downstream from the environment. [15] With warmer temperatures, rapid snowmelt will lead to a greater concentration of contaminants entering the stream at once. [15]

Stream Monitoring

Macroinvertebrates (eg. midges) are indicator species and are often examined to determine how humans are affecting the ecosystem. [16] Unfortunately, insufficient research has been conducted for the environmental preferences of macroinvertebrates in alpine environments, increasing the difficulty of monitoring the changes in glacial streams. [16]

Related Research Articles

<span class="mw-page-title-main">Glacier</span> Persistent body of ice that is moving under its own weight

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 crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

<span class="mw-page-title-main">Moraine</span> Glacially formed accumulation of debris

A moraine is any accumulation of unconsolidated debris, sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet. It may consist of partly rounded particles ranging in size from boulders down to gravel and sand, in a groundmass of finely-divided clayey material sometimes called glacial flour. Lateral moraines are those formed at the side of the ice flow, and terminal moraines were formed at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines and medial moraines.

<span class="mw-page-title-main">Till</span> Unsorted glacial sediment

Till or glacial till is unsorted glacial sediment.

<span class="mw-page-title-main">Glaciology</span> Scientific study of ice and natural phenomena involving ice

Glaciology is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.

<span class="mw-page-title-main">Jökulhlaup</span> Type of glacial outburst flood

A jökulhlaup is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland, which are triggered by geothermal heating and occasionally by a volcanic subglacial eruption, but it is now used to describe any large and abrupt release of water from a subglacial or proglacial lake/reservoir.

<span class="mw-page-title-main">Glacial erratic</span> Piece of rock that has been moved by a glacier

A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word errare, are carried by glacial ice, often over distances of hundreds of kilometres. Erratics can range in size from pebbles to large boulders such as Big Rock in Alberta.

<span class="mw-page-title-main">Glacial lake</span> Lake formed by a melted glacier

A glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land and then melts, filling the depression created by the glacier.

<span class="mw-page-title-main">Subglacial lake</span> Lake under a glacier

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 of ice. Over time, the overlying ice gradually melts at a rate of a few millimeters per year. Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years.

<span class="mw-page-title-main">Terminal moraine</span> Type of moraine that forms at the terminal of a glacier

A terminal moraine, also called an end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge of the ice, is driven no further and instead is deposited in an unsorted pile of sediment. Because the glacier acts very much like a conveyor belt, the longer it stays in one place, the greater the amount of material that will be deposited. The moraine is left as the marking point of the terminal extent of the ice.

<span class="mw-page-title-main">Tunnel valley</span> Glacial-formed geographic feature

A tunnel valley is a U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages. They can be as long as 100 km (62 mi), 4 km (2.5 mi) wide, and 400 m (1,300 ft) deep.

<span class="mw-page-title-main">Meltwater</span> Water released by the melting of snow or ice

Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found during early spring when snow packs and frozen rivers melt with rising temperatures, and 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 lahars form.

<span class="mw-page-title-main">Subglacial eruption</span> Eruption of an ice-covered volcano

Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volcanic areas, including Iceland, Alaska, and parts of the Andes. Jökulhlaups have been identified as the most frequently occurring volcanic hazard in Iceland, with major events where peak discharges of meltwater can reach 10,000 – 100,000 m3/s occurring when there are large eruptions beneath glaciers.

A subaqueous fan is a fan-shaped deposit formed beneath water, and are commonly related to glaciers and crater lakes.

Fluvioglacial landforms are those that result from the associated erosion and deposition of sediments caused by glacial meltwater. These landforms may also be referred to as glaciofluvial in nature. Glaciers contain suspended sediment loads, much of which is initially picked up from the underlying landmass. Landforms are shaped by glacial erosion through processes such as glacial quarrying, abrasion, and meltwater. Glacial meltwater contributes to the erosion of bedrock through both mechanical and chemical processes.

<span class="mw-page-title-main">Supraglacial lake</span> Pond of liquid water on the top of a glacier

A supraglacial lake is any pond of liquid water on the top of a glacier. Although these pools are ephemeral, they may reach kilometers in diameter and be several meters deep. They may last for months or even decades at a time, but can empty in the course of hours.

<span class="mw-page-title-main">Ice-sheet dynamics</span> Technical explanation of ice motion within large bodies of ice

Ice sheet dynamics describe the motion within large bodies of ice such as those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity-driven activity is controlled by two main variable factors: the temperature and the strength of their bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on both hourly and centennial time scales. Ice-sheet dynamics are of interest in modelling future sea level rise.

<span class="mw-page-title-main">Overdeepening</span> Characteristic of basins and valleys eroded by glaciers

Overdeepening is a characteristic of basins and valleys eroded by glaciers. An overdeepened valley profile is often eroded to depths which are hundreds of metres below the lowest continuous surface line along a valley or watercourse. This phenomenon is observed under modern day glaciers, in salt-water fjords and fresh-water lakes remaining after glaciers melt, as well as in tunnel valleys which are partially or totally filled with sediment. When the channel produced by a glacier is filled with debris, the subsurface geomorphic structure is found to be erosionally cut into bedrock and subsequently filled by sediments. These overdeepened cuts into bedrock structures can reach a depth of several hundred metres below the valley floor.

Subglacial streams are conduits of glacial meltwater that flow at the base of glaciers and ice caps. Meltwater from the glacial surface travels downward throughout the glacier, forming an englacial drainage system consisting of a network of passages that eventually reach the bedrock below, where they form subglacial streams. Subglacial streams form a system of tunnels and interlinked cavities and conduits, with water flowing under extreme pressures from the ice above; as a result, flow direction is determined by the pressure gradient from the ice and the topography of the bed rather than gravity. Subglacial streams form a dynamic system that is responsive to changing conditions, and the system can change significantly in response to seasonal variation in meltwater and temperature. Water from subglacial streams is routed towards the glacial terminus, where it exits the glacier. Discharge from subglacial streams can have a significant impact on local, and in some cases global, environmental and geological conditions. Sediments, nutrients, and organic matter contained in the meltwater can all influence downstream and marine conditions. Climate change may have a significant impact on subglacial stream systems, increasing the volume of meltwater entering subglacial drainage systems and influencing their hydrology.

A meltwater channel is a channel cut into ice, bedrock or unconsolidated deposits by the flow of water derived from the melting of a glacier or ice-sheet. The channel may form on the surface of, within, beneath, along the margins of or downstream from the ice mass. Accordingly it would be referred to as supraglacial, englacial, subglacial, lateral or proglacial.

<span class="mw-page-title-main">Glaciofluvial deposits</span> Sediments/deposits formed from ice sheets or glaciers

Glaciofluvial deposits or Glacio-fluvial sediments consist of boulders, gravel, sand, silt and clay from ice sheets or glaciers. They are transported, sorted and deposited by streams of water. The deposits are formed beside, below or downstream from the ice. They include kames, kame terraces and eskers formed in ice contact and outwash fans and outwash plains below the ice margin. Typically the outwash sediment is carried by fast and turbulent fluvio-glacial meltwater streams, but occasionally it is carried by catastrophic outburst floods. Larger elements such as boulders and gravel are deposited nearer to the ice margin, while finer elements are carried farther, sometimes into lakes or the ocean. The sediments are sorted by fluvial processes. They differ from glacial till, which is moved and deposited by the ice of the glacier, and is unsorted.

References

  1. 1 2 3 United States Geological Survey. "Glossary of Glacier Terminology" . Retrieved 2021-03-26.
  2. 1 2 3 4 5 6 Chu, Vena (2014-11-26). "Greenland ice sheet hydrology: A review". Progress in Physical Geography. 38: 19–54. doi:10.1177/0309133313507075. S2CID   56217787.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 St Germain, Sarah L.; Moorman, Brian J. (2019). "Long-term observations of supraglacial streams on an Arctic glacier". Journal of Glaciology. 65 (254): 900–911. Bibcode:2019JGlac..65..900S. doi: 10.1017/jog.2019.60 . ISSN   0022-1430.
  4. 1 2 3 "How Glaciers Change the Landscape (U.S. National Park Service)". www.nps.gov. Retrieved 2021-03-26.
  5. ↑ Fahnestock, Robert K. (1963). "Morphology and Hydrology of a Glacial Stream - White River, Mount Rainier Washington" (PDF). Retrieved 2021-03-26.
  6. 1 2 "How do glaciers affect land? | National Snow and Ice Data Center". nsidc.org. Retrieved 2021-03-26.
  7. 1 2 3 Mao, L.; Dell'Agnese, A.; Comiti, F. (2017-08-15). "Sediment motion and velocity in a glacier-fed stream". Geomorphology. 291: 69–79. Bibcode:2017Geomo.291...69M. doi:10.1016/j.geomorph.2016.09.008. ISSN   0169-555X.
  8. 1 2 3 4 5 6 7 8 9 Uehlinger, U.; Robinson, C. T.; Hieber, M.; Zah, R. (2010). "The physico-chemical habitat template for periphyton in alpine glacial streams under a changing climate". Hydrobiologia. 657 (1): 107–121. doi:10.1007/s10750-009-9963-x. hdl: 20.500.11850/23355 . ISSN   1573-5117. S2CID   24352757.
  9. 1 2 3 Koch, J. C.; McKnight, D. M.; Neupauer, R. M. (2011). "Simulating unsteady flow, anabranching, and hyporheic dynamics in a glacial meltwater stream using a coupled surface water routing and groundwater flow model". Water Resources Research. 47 (5): W05530. Bibcode:2011WRR....47.5530K. doi: 10.1029/2010WR009508 . ISSN   1944-7973.
  10. 1 2 3 4 5 6 Füreder, Leopold; Niedrist, Georg H. (2020). "Glacial Stream Ecology: Structural and Functional Assets". Water. 12 (2): 376. doi: 10.3390/w12020376 . ISSN   2073-4441.
  11. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Ward, J.V. (1994). "Ecology of alpine streams". Freshwater Biology. 32 (2): 277–294. doi:10.1111/j.1365-2427.1994.tb01126.x. ISSN   0046-5070.
  12. ↑ McGregor, G.; Petts, G. E.; Gurnell, A. M.; Milner, A. M. (1995). "Sensitivity of alpine stream ecosystems to climate change and human impacts". Aquatic Conservation: Marine and Freshwater Ecosystems. 5 (3): 233–247. doi:10.1002/aqc.3270050306. ISSN   1052-7613.
  13. 1 2 Hood, Eran; Berner, Logan (2009). "Effects of changing glacial coverage on the physical and biogeochemical properties of coastal streams in southeastern Alaska". Journal of Geophysical Research: Biogeosciences. 114 (G3): G03001. Bibcode:2009JGRG..114.3001H. doi: 10.1029/2009JG000971 . ISSN   2156-2202.
  14. 1 2 Rizzi, C.; Finizio, A.; Maggi, V.; Villa, S. (2019). "Spatial-temporal analysis and risk characterisation of pesticides in Alpine glacial streams". Environmental Pollution. 248: 659–666. doi:10.1016/j.envpol.2019.02.067. hdl: 10281/222920 . PMID   30849583. S2CID   73513638.
  15. 1 2 3 Bizzotto, E. C.; Villa, S.; Vaj, C.; Vighi, M. (2009). "Comparison of glacial and non-glacial-fed streams to evaluate the loading of persistent organic pollutants through seasonal snow/ice melt". Chemosphere. 74 (7): 924–930. Bibcode:2009Chmsp..74..924B. doi:10.1016/j.chemosphere.2008.10.013. ISSN   0045-6535. PMID   19054540.
  16. 1 2 Niedrist, Georg H.; Füreder, Leopold (2016). "Towards a definition of environmental niches in alpine streams by employing chironomid species preferences". Hydrobiologia. 781 (1): 143–160. doi: 10.1007/s10750-016-2836-1 . ISSN   1573-5117.
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