Reeves, Katherine and Gilbert, Jennie and Lane, Stephen and Leeson, Amber (2022) Supraglacial and englacial particle-ice interaction in dirty ice conditions. PhD thesis, Lancaster University.
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Abstract
Particles can modify the thermodynamic behaviour of ice in response to insolation. Ice with surface particles is defined as ‘debris-covered’ or ‘dirty’ ice, depending on whether a continuous or discontinuous layer is present, respectively. The behaviour of dirty ice has not been extensively researched, although these ice conditions are common. Improving our understanding of discontinuous particle-ice interaction can aid forecasting of ice changes in a warming world. Laboratory experiments were designed to address knowledge gaps in the behaviour of: (1) particle properties (thermal conductivity, albedo, density, and diameter) on influencing particle-ice interaction using control particles, such as plastics (e.g. polystyrene) and metals (e.g. brass and chrome steel); (2) volcanic particles (e.g. basaltic scoria and rhyolitic pumice) in dirty ice conditions; and (3) microplastic particles (e.g. polyethylene and polypropylene) in dirty ice conditions. Particle-ice interaction under analogue insolation (80 W LED) was studied in conditions analogous to the supraglacial and englacial environment, at scales ranging from individual particles to a scattering of particles, all with a diameter Results demonstrated that dirty ice conditions are significant for glacier ablation, with a range of particle-ice behaviours observed: (1) sinking particles created melt channels within ice; (2) floating particles created surface meltwater ponds with surface tension effects facilitating particle redistribution processes; (3) particles utilised pre-existing internal ice structures (e.g. vein networks) as ablation pathways; and (4) volcanic particle fragmentation. These were controlled by the thermal state of ice, and particle properties. The englacial environment was additionally found to be significant for ablation. The laboratory behaviour of volcanic and microplastic particles compared well with behaviours estimated through systematic investigation of particle properties, suggesting that the fate of particles within ice can be mapped through assessment of particle properties.