Ultrasonic Velocity Investigations of Crystal Anisotropy in Deep Ice Cores from Antarctica

Ice cores from Byrd Station and Little America V have been used to test an ultrasonic technique for evaluating crystal anisotropy in the Antarctic Ice Sheet. P-wave velocities measured parallel and perpendicular to the vertical axes of cores from the 2164-m-thick ice sheet at Byrd Station have yield...

Full description

Bibliographic Details
Main Authors: Kohnen,Heinz, Gow,Anthony J
Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
Format: Text
Language:English
Published: 1979
Subjects:
Snow
Ice and Permafrost
*ANISOTROPY
*LAND ICE
MEASUREMENT
CRYSTAL STRUCTURE
CORES
ANTARCTIC REGIONS
ULTRASONIC RADIATION
Antarctic
Byrd
Byrd Station
Little America
Little America V
The Antarctic
Antarc*
Antarctica
Ice
Ice Sheet
permafrost
Online Access:http://www.dtic.mil/docs/citations/ADA071451
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA071451
Description
Summary:Ice cores from Byrd Station and Little America V have been used to test an ultrasonic technique for evaluating crystal anisotropy in the Antarctic Ice Sheet. P-wave velocities measured parallel and perpendicular to the vertical axes of cores from the 2164-m-thick ice sheet at Byrd Station have yielded results in excellent agreement with the observed c-axis fabric profile and with the in-situ P-wave velocity profile measured parallel to the bore hole axis. Velocity differences in excess of 140 m/s for core samples from deeper than 1300 m attest to the strong single pole clustering of crystallographic c-axes about the vertical, especially in the zone from 1300-1800 m. Such oriented structure is compatible only with strong horizontal shearing in this zone. The existence in an ice sheet of widespread shearing several hundred meters above its bed raises serious questions as to the validity of current concepts of the flow of large ice masses that tend to gloss over or ignore crystal alignments of this magnitude.

Similar Items