Meltwater channels in a glacial environment are considered an erosional feature that’s part of the landscape geomorphology. They are what has been carved out and left behind in the landscape, by the force and strength of the water flow in a drainage pathway (Shaw & Sharpe, 1987). The effect of pressurised water on the proglacial areas and the hydrology of glaciers exerts a strong influence on different characteristics of the glacier, and meltwater channels are evidence of this. Where meltwater channels carve from glacier margins to the sea the land is forcefully shaped, this influences rates of erosions, glacier movement and the deposition of glacial till. (Benn & Evans, 2010). It is this imprint of meltwater channels left behind in the landscape that allows scientists to conduct the challenging yet effective task of glacier reconstruction.
The aim of this paper is to review the formation and presence of meltwater channels in glacial landscapes and determine their eligibility in glacier reconstruction.
Before going any further it’s important to note the difference between drainage pathways and meltwater channels. Drainage pathways are the route through a glacier which the water has taken. These pathways are part of complex drainage systems of the transportation of water within an dentritic network. (Singh, Singh & Haritashya, 2011). Meltwater channels are the landform left behind once the water has drained away. It is this that tells scientists about past glaciation.
An understanding of the formation of these drainage pathways must be exhibited to understand the formation of meltwater channels. The changes in state of ice due to the global energy exchange between surface ice and the atmosphere, can bring about surface melting. This is when there is a surplus of solar energy when the temperature of the ice is 0ᵒC (Benn & Evans, 2010). Subglacial melting occurs due to the development of high pressure at the glacier base as it flows over bedrock. This basal sliding causes frictional heating and can lead to changes to the shape of the glacier (Goudie, 2004). Geothermal heating from beneath the ice also causes melting. An example of this process occurring is in the West Antarctic where the Pine Island Glacier is melting from heat produced from a volcanic rift system below the surface (Watts, 2014). These heat processes are the primary causes of ablation in glacial systems(Goudie, 2004)
Formation of Meltwater Channels
Meltwater channels are classed as mesoscale landforms and are formed as a result of glacial erosion. The two main types of meltwater channels formed from this process are subglacial and lateral. When crevasses develop within the glacier due to extensional flow, water can travel down to a subglacial position via a moulin. This meltwater erodes the bedrock to carve out a subglacial meltwater channel. As the water erodes downwards into the sediment it firstly creates an N-channel, a landform associated with meltwater channels (Bennett & Glasser,2009). Subglacial channels are mainly formed in temperate glaciers and the N-channel that forms can be a single channel or a network of channels (Singh, Singh & Haritashya, 2011). Lateral meltwater channels run along the margin of the glacier at a shallow angle to the slope (Unknown, 2014). In contrast to subglacial meltwater channels, they generally form at cold-based glaciers. These glaciers are frozen to the substrate preventing the infiltration of water, therefore water is forced to travel down the side of the glacier. Here it erodes the margin leaving behind a lateral meltwater channel (Singh, Singh & Haritashya, 2011).
The formation of these meltwater channels is influenced by hydraulic potential. This occurs when water is not flowing freely due to atmospheric pressure under the influence of gravity, but when water flow is driven by at potential gradient (Knight, 2006). In terms of subglacial channels the pressure of the water under the ice mass can cause water to flow uphill giving the channel a humped profile. (Singh, Singh & Haritashya, 2011). Thermal regime influences the temperature of the ice. It is a function corresponding with air and ground temperatures as well as geothermal heating that controls whether the glacier will be warm based such as the Alps in temperate regions, or cold based like many in Antarctica. It is this difference in temperature that occasionally leads to the formation of either lateral or subglacial channels (Davies, 2014)
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