27 Feb 2023
 | 27 Feb 2023
Status: this preprint is open for discussion.

Partial melting in polycrystalline ice: Pathways identified in 3D neutron tomographic images

Christopher Wilson, Mark Peternell, Filomena Salvemini, Vladimir Luzin, Frieder Enzmann, Olga Moravcova, and Nicholas Hunter

Abstract. In frozen cylinders composed of deuterium ice (Tm+3.8 ºC) and 10 % water ice (Tm 0 ºC) it is possible to track melt pathways produced by increasing the temperature during deformation. Raising the temperature to +2 ºC produces water (H2O) which combines with the D2O ice to form mixtures of HDO. As a consequence of deformation, HDO and H2O meltwater are expelled along conjugate shear bands and as compactional melt segregations. Melt segregations are also associated with high porosity networks related to the location of transient reaction fronts where the passage of melt-enriched fluids is controlled by the localized ductile yielding and lowering of the effective viscosity. Accompanying the softening, the meltwater also changes and weakens the crystallographic fabric development of the ice. Our observations suggest meltwater-enriched compaction and shear band initiation provides instabilities and the driving force for an enhancement of permeability in terrestrial ice sheets and glaciers.

Christopher Wilson et al.

Status: open (until 01 May 2023)

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Christopher Wilson et al.

Christopher Wilson et al.


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Short summary
As the temperature increases within a deforming ice aggregate, composed of deuterium (D2O) ice and water (H2O) ice, a set of meltwater segregations are produced. These are composed of H2O and HDO and are located in conjugate shear bands and in compaction bands which accommodate the deformation and weaken the ice aggregate. This has major implications for the passage of meltwater in ice sheets and the formation of the layering recognized in glaciers.