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Title: Soil erosion and transport by needle ice : a laboratory investigation
Author: Branson, Julia
ISNI:       0000 0004 2727 5872
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 1993
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A series of detailed laboratory experiments have been carried out to investigate the processes of needle-ice growth and the mechanisms by which needle ice incorporates and transports sediment. The use of laboratory techniques has made it possible to control and monitor the environmental conditions at the soil surface closely, and thus isolate the elements that are important for needle ice growth. Two types of fine-grained soil sample were used: disturbed (remoulded) and undisturbed. These were taken from sites where needle ice was seen to grow naturally. Remoulding the soil sample affected the growth of needle ice and therefore the amount of sediment uplifted by the ice. Several types of needle ice were observed: clear, multitiered, crystals with dispersed sediment, soil caps and soil aggregates. Each type was produced under different conditions of soil-surface temperature and moisture. Soil-moisture availability was particularly important in controlling the type and rate of crystal growth. An algorithm has been developed with which to predict the type of crystal that will grow in a given freezing cycle. It is suggested that sediment becomes incorporated into the crystals when there is a disturbance in the environment of needle-ice growth. This disturbance is a result of instabilities in the balance of heat at the freezing front caused when either soil-surface temperature or soil-moisture content fall below a minimum threshold. Typical sediment yields ranged from 0.002 to 2.5 g cm\(^-\)\(^2\). The sediment incorporated into the needle-ice crystals was coarser than the bulk soil from which it was lifted. The transport of sediment by needle ice was also investigated. It was found that the distance of sediment transport is dependent on the slope angle, length of ice crystal, process of crystal melt, and type of marker particle and soil sample. A series of simple, statistical models is presented that attempts to predict the growth and morphological effects of needle ice.
Supervisor: Not available Sponsor: Natural Environment Research Council (NERC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: GB Physical geography ; GE Environmental Sciences