Item: Formation of Depth Hoar Resulting from Thermal Optimization of Snow Microstructure
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Title: Formation of Depth Hoar Resulting from Thermal Optimization of Snow Microstructure
Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska
Authors:
- Patrick J. Staron [ Department of Civil Engineering, Monta na State University, Bozeman, Montana, USA ]
- Edward E. Adams [ Department of Civil Engineering, Monta na State University, Bozeman, Montana, USA ]
- Daniel A. Miller [ Department of Civil Engineering, Monta na State University, Bozeman, Montana, USA ]
Date: 2012
Abstract: Snow metamorphism can be described by the flows of heat and mass that result from gradients of temperature and water vapor concentration. The size of the forcing gradient necessary to induce the corresponding flow is a measure of the system efficiency. Kinetic metamorphism is a process of thermodynamic optimization in which the microstructure and material properties evolve to increase the heat transport efficiency. The optimal geometric configuration is a system of well-connected ice columns oriented in the direction of the heat flow. This morphology is commonly referred to as depth hoar and is a persistent weak layer that is frequently responsible for avalanches. A series of laboratory experiments were conducted to examine the evolution of snow microstructure. Fresh snow was subjected to either constant temperature gradient or constant heat flux boundary conditions to produce an upward vertical heat flow through the sample. For all experiments, the effective thermal conductivity increased in the direction of heat flow, and the ratio of heat conduction to latent heat transfer increased with the formation of ice chains. By naturally improving the conductivity of the ice network and directing more thermal energy through the ice, the system became more efficient. This progression resulted from the system and its surroundings moving toward equilibrium in accordance with the second law of thermodynamics. Thus the formation of depth hoar, often responsible for destructive deep slab avalanches, is due to a natural optimization of the conduction pathways through the snow.
Object ID: issw-2012-186-193.pdf
Language of Article: English
Presenter(s): unknown
Keywords: entropy, metamorphism, microstructure, optimization, snow, thermodynamics
Page Number(s): 186-193
Subjects: snow metamorphism deep slab avalanche
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