DEEP CORE STUDIES OF THE CRYSTAL STRUCTURE AND FABRICS OF ANTARCTIC GLACIER ICE.

• Main Author: Gow,Anthony J.
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER N H
• Format: Text
• Language: English
• Published: 1970
• Subjects: Snow; Ice and Permafrost; Crystallography; (*CRYSTAL STRUCTURE; ICE); (*ICE; ANTARCTIC REGIONS); GLACIERS; SAMPLING; DRILLING; CRYSTAL GROWTH; DEFORMATION; STRUCTURAL PROPERTIES; MELTING; THICKNESS; BYRD STATION(ANTARCTICA); ROSS ICE SHELF; DRILL CORE ANALYSIS; Antarctic; Byrd; Byrd Station; Little America; Little America V; Ross Ice Shelf; Antarc*; Antarctica; Ice; Ice Sheet; Ice Shelf; permafrost
• Online Access: http://www.dtic.mil/docs/citations/AD0704348; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0704348

Radical differences in the crystal structure and fabrics of glacier ice cores at Byrd Station and Little America V, Antarctica, are attributed to gross differences in the thermal and deformational histories of the ice at these two locations. At Byrd Station the mean size of crystals increased more than sixfold between 65 meters and the bottom of the drill hole at 309 meters. Crystal size was also found to increase linearly with the age of the ice, thus simulating isothermal grain growth in metals. However, this growth was not accompanied by any dimensional orientation of crystals or entrapped bubbles, or by any significant increase in the degree of preferred orientation of crystallographic c-axes. These observations imply that negligible shearing is occurring in the top 300 meters of the thick grounded ice sheet at Byrd Station. By contrast very considerable deformation is indicated for the floating 258-m-thick Ross Ice Shelf at Little America. This deformation is characterized by the widespread occurrence of 'strained' crystals below 65 meters, the existence of elongated orineted bubbles between 95 meters and 130 meters and the attainment of pronounced crystal orientation (multiple-maxima fabrics) by 100-meters depth. Exaggerated growth of crystals below 150 meters is atrributed to increasing temperatures in the ice shelf. The crystal structure of these cores clearly demonstrates that glacial ice only is present in the Ross Ice Shelf at Little America V. (Author) Sponsored in part by National Science Foundation, Washington, D. C.