Microstructures and Fabric Transitions of Natural Ice from the Styx Glacier, Northern Victoria Land, Antarctica

Daeyeong Kim,Hyeon Tae Ju,Yeongcheol Han,David J Prior,Chao Qi,Hyangsun Han

doi:10.3390/min10100892

Daeyeong Kim, Hyeon Tae Ju + Show 4 more

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https://doi.org/10.3390/min10100892

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Abstract

We investigated the microstructures of five ice core samples from the Styx Glacier, northern Victoria Land, Antarctica. Evidence of dynamic recrystallization was found in all samples: those at 50 m mainly by polygonization, and those at 170 m, largely by grain boundary migration. Crystallographic preferred orientations of all analyzed samples (view from the surface) typically showed a single cluster of c-axes normal to the surface. A girdle intersecting the single cluster occurs at 140–170 m with a tight cluster of a-axes normal to the girdle. We interpret the change of crystallographic preferred orientations (CPOs) at <140 m as relating to a combination of vertical compression, and shear on a horizontal plane, and the girdle CPOs at depths >140 m, as the result of horizontal extension. Based on the data obtained from the ground penetrating radar, the underlying bedrock topography of a nunatak could have generated the extensional stress regime in the study area. The results imply changeable stress regimes that may occur during burial as a result of external kinematic controls, such as an appearance of a small peak in the bedrock.

Highlights

Understanding the rheological behavior of Antarctic ice is essential for predictions of sea-level change in the future
From depths of 50–170 m by a core drilled in the Styx Glacier, located in northern Victoria Land, In the study area, the evolution of the crystallographic preferred orientations (CPOs) from a single cluster of c-axes to a single cluster with
The formation of the girdle that accompanied the strong single cluster is kinematically distinct locations within ice sheets. This process is crucial for a thorough review of the characterized by an abrupt increase in fabric indices, and a decrease in the shape factor; conventional ice flow models

Summary

Introduction

Understanding the rheological behavior of Antarctic ice is essential for predictions of sea-level change in the future. The flow of ice is usually controlled by two processes: frictional sliding on the bedrock, which often occurs where the base is at pressure melting or pre-melting conditions [1,2,3,4,5,6,7,8], and the internal plastic deformation of the polycrystalline ice [9,10,11,12,13,14,15]. The plastic deformation of Antarctic ice results in the development of crystallographic preferred orientations (CPOs), which may induce a strong mechanical anisotropy that can enhance or impede the flow of ice and can be used to study the kinematics of flow [16]. Usually three types of ice c-axes fabrics form: single cluster, double clusters, and a girdle.

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