Essay: Formation and presence of meltwater channels in glacial landscapes (Page 2 of 2)

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Their capability in reconstruction

Palaeo ice sheet reconstruction of glacier extent and dynamics is off great importance to scientists because it gives them an idea of the climatic sensitivity of past glaciers and the role of erosional and depositional process caused by meltwater flow. This flow can influence the transfer of ice mass which in turn will enable scientists to determine glacial retreat history (Carr & Coleman, 2007). Other aspects of glacial reconstruction that meltwater channels provide is the thermal regime and patterns of former ice streams. In general the task of reconstruction will allow for a better understanding of the earth system, former climate and future sea level change.

The use of meltwater channels in the past has enabled successful reconstruction of the Pleistocene British Ice Sheet. By mapping channel distribution these channels have showed past glaciological conditions, the process of deglaciation and identified different channel types and flow patterns (Singh, Singh & Haritashya, 2011).

Landforms associated with meltwater channels can indicate glacier retreat history as they are usually formed during the retreat stage. Erosional landforms include the channel itself, glacial lakes and fossil shorelines while depositional landforms include outwashed fans and eskers. Together with ice dynamics such as glacial lineations and moraines, these give an idea of the deglaciation stage particularly the direction of retreat (Marigold, 2012). It has also been discovered that channels flow parallel to ice flow (Unknown, 2014). As a glacier looses mass it can erode into the landscape to create a notch. As the glacier retreats this process continues to create a sequence of notches to reveal lateral channels within the landscape as well as provide an indication of the nature of retreat. This process is not associated with modern fluvial drainage and it has generally been found that glacial meltwater channels don’t follow the same flow pattern of modern channels today. This is shown in figure 5. A reason for this as mentioned is the humped profile of meltwater channels caused by the flow of pressurised water (Benn & Evans, 2010)

The thermal regime of glaciers can also be identified by meltwater channels. As identified cold based glaciers are generally associated with lateral meltwater channels. These channels can also tell scientists the retreat of margins and former polythermal glacier margins. In Canadian and Greenland High Arctic these have been extensively marked by lateral meltwater channels and have shown glacier recession (Benn & Evans, 2010). On the other hand warm based glaciers are characterised by sub glacial meltwater channels. Glacial lakes can also be associated with warm based glaciers and are an important feature in identifying glacial retreat history (Marigold, 2012).

Conclusion

Despite the reconstruction potential of meltwater channels, there are some limitations of their use in the models and methodology of reconstruction. A study using remotely sensed data and digital elevation models was conducted in northern Finland, that used meltwater channels to indentify fossil glacial lake shorelines. The remote sensing data did not recognised any shorelines even though this area is known to consist of them (Marigold, 2012) Data on reconstruction is scarce with reliance on the evidence collected and interpreted by other scientists. Glacial reconstruction of the iconic Laurentide Ice Sheet has been conducted in the past by Boulton and Clark in 1990 with the use of Landsat MSS imagery and aerial photographs. They were able to reconstruct the evolution of the ice sheet but made no effort to include marginal channels and meltwater landforms in its reconstruction (Knight, 2006). With the complexity of glacier reconstruction it is evident that plausible data collection must be carried out in a rigorous manner in order to be reliable. The vast potential of the use meltwater channels in reconstruction must be considered in future studies.

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