scholarly journals Measurement of vertical strain and velocity at Siple Dome, Antarctica, with optical sensors

2002 ◽  
Vol 48 (161) ◽  
pp. 217-225 ◽  
Author(s):  
Mark A. Zumberge ◽  
Daniel H. Elsberg ◽  
William D. Harrison ◽  
Eric Husmann ◽  
John L. Morack ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Optical Sensors ◽  
Ice Sheet ◽  
Hot Water ◽  
Constitutive Relationship ◽  
Strain Rates ◽  
Thin Wall ◽  
Vertical Strain ◽  
The North ◽  
Siple Dome

AbstractAs part of a larger program to measure and model vertical strain around Siple Dome on the West Antarctic ice sheet, we developed a new sensor to accurately and stably record displacements. The sensors consist of optical fibers, encased in thin-wall stainless-steel tubes, frozen into holes drilled with hot water, and stretched from the surface to various depths (up to 985 m) in the ice sheet. An optical system, connected annually to the fibers, reads out their absolute lengths with a precision of about 2 mm. Two sets of five sensors were installed in the 1997/98 field season: one set is near the Siple Dome core hole (an ice divide), and a second set is on the flank 7 km to the north (the ice thickness at both sites is approximately 1000 m). The optical-fiber length observations taken in four field seasons spanning a 3 year interval reveal vertical strain rates ranging from −229 ± 4 ppm a−1 to −7 ± 9 ppm a−1. In addition to confirming a non-linear constitutive relationship for deep ice, our analysis of the strain rates indicates the ice sheet is thinning at the flank and is in steady state at the divide.

scholarly journals Depth- and time-dependent vertical strain rates at Siple Dome, Antarctica

2004 ◽  
Vol 50 (171) ◽  
pp. 511-521 ◽  
Author(s):  
Daniel H. Elsberg ◽  
William D. Harrison ◽  
Mark A. Zumberge ◽  
John L. Morack ◽  
Erin C. Pettit ◽  
...  
Keyword(s):  
Strain Rate ◽  
Time Dependence ◽  
Strain Gauge ◽  
Water Pressure ◽  
Time Dependent ◽  
Strain Rates ◽  
Ice Streams ◽  
Vertical Strain ◽  
Siple Dome ◽  
A Site

AbstractAs part of a project to investigate the flow of ice at low effective stress, two independent strain-gauge systems were used to measure vertical strain rate as a function of depth and time at Siple Dome, Antarctica. The measurements were made from January 1998 until January 2002 at the ice divide and a site 7km to the northeast on the flank. The strain-rate profiles place constraints on the rheology of ice at low stress, show the expected differences between divide and flank flow (with some structure due to firn compaction and probably ice stratigraphy), and suggest that the flow of the ice sheet has not changed much in the last 8.6 kyr. The strain rates show an unexpected time dependence on scales ranging from several months to hours, including discrete summer events at the divide. Time dependence in strain rate, water pressure, seismicity, velocity and possibly basal motion has been seen previously on the Siple Coast ice streams, but it is especially surprising on Siple Dome because the bed is cold.

scholarly journals A ground-based radar for measuring vertical strain rates and time-varying basal melt rates in ice sheets and shelves

2015 ◽  
Vol 61 (230) ◽  
pp. 1079-1087 ◽  
Author(s):  
Keith W. Nicholls ◽  
Hugh F.J. Corr ◽  
Craig L. Stewart ◽  
Lai Bun Lok ◽  
Paul V. Brennan ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Present System ◽  
Strain Rates ◽  
Time Varying ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Vertical Strain ◽  
Phase Sensitive

AbstractThe ApRES (autonomous phase-sensitive radio-echo sounder) instrument is a robust, lightweight and relatively inexpensive radar that has been designed to allow long-term, unattended monitoring of ice-shelf and ice-sheet thinning. We describe the instrument and demonstrate its capabilities and limitations by presenting results from three trial campaigns conducted in different Antarctic settings. Two campaigns were ice sheet-based – Pine Island Glacier and Dome C – and one was conducted on the Ross Ice Shelf. The ice-shelf site demonstrates the ability of the instrument to collect a time series of basal melt rates; the two grounded ice applications show the potential to recover profiles of vertical strain rate and also demonstrate some of the limitations of the present system.

scholarly journals Dating firn cores by vertical strain measurements

2002 ◽  
Vol 48 (162) ◽  
pp. 401-406 ◽  
Author(s):  
Robert L. Hawley ◽  
Edwin D. Waddington ◽  
David L. Morse ◽  
Nelia W. Dunbar ◽  
Gregory A. Zielinski
Keyword(s):  
Ice Core ◽  
Video Camera ◽  
Strain Rates ◽  
West Antarctica ◽  
Polar Ice ◽  
Vertical Strain ◽  
Ash Layer ◽  
Siple Dome ◽  
Polar Ice Sheets ◽  
Rate Profile

AbstractWe have developed a system for measuring a vertical strain-rate profile in the firn on polar ice sheets using a readily available video camera to detect metal bands inserted in an air-filled hole. We used this system in 1995 and 1996 at Taylor Dome, Antarctica. We use density measurements combined with our strain rates to infer vertical velocities. From our velocities we calculate a steady-state depth–age scale for the firn at Taylor Dome. The age of a visible ash layer from 79.1 m is 675 ± 25 years; this ash can be correlated with ash found at 97.2 m in a recent ice core at Siple Dome, West Antarctica.

High-voltage monitoring by the fiber-optic recirculating measuring system

2020 ◽  
pp. 38-44
Author(s):  
A. V. Polyakov ◽  
M. A. Ksenofontov
Keyword(s):  
Optical Fibers ◽  
High Voltage ◽  
Optical Sensors ◽  
Electromagnetic Interference ◽  
Fiber Optic ◽  
Electric Power Industry ◽  
Measuring System ◽  
Voltage Range ◽  
External Electromagnetic Fields ◽  
Optic Communication

Optical technologies for measuring electrical quantities attract great attention due to their unique properties and significant advantages over other technologies used in high-voltage electric power industry: the use of optical fibers ensures high stability of measuring equipment to electromagnetic interference and galvanic isolation of high-voltage sensors; external electromagnetic fields do not influence the data transmitted from optical sensors via fiber-optic communication lines; problems associated with ground loops are eliminated, there are no side electromagnetic radiation and crosstalk between the channels. The structure and operation principle of a quasi-distributed fiber-optic high-voltage monitoring system is presented. The sensitive element is a combination of a piezo-ceramic tube with an optical fiber wound around it. The device uses reverse transverse piezoelectric effect. The measurement principle is based on recording the change in the recirculation frequency under the applied voltage influence. When the measuring sections are arranged in ascending order of the measured effective voltages relative to the receiving-transmitting unit, a relative resolution of 0,3–0,45 % is achieved for the PZT-5H and 0,8–1,2 % for the PZT-4 in the voltage range 20–150 kV.

scholarly journals The North Sea Ice Sheet

Nature ◽  
1894 ◽  
Vol 50 (1282) ◽  
pp. 79-79
Author(s):  
HENRY H. HOWORTH
Keyword(s):  
Sea Ice ◽  
North Sea ◽  
Ice Sheet ◽  
The North ◽  
The North Sea

Volcanic History and Tectonics of the North Langjökull Region, Central Iceland

1973 ◽  
Vol 10 (2) ◽  
pp. 164-179 ◽  
Author(s):  
J. D. A. Piper
Keyword(s):  
Late Pleistocene ◽  
Volcanic Activity ◽  
Active Zone ◽  
Ice Sheet ◽  
North Coast ◽  
Crustal Growth ◽  
Transform Fault ◽  
Active Volcanism ◽  
The North ◽  
Lava Pile

The geology of the area around the northern part of the Langjökull ice sheet in central Iceland is outlined. This area includes the termination of the western neovolcanic zone, two silicic centers, and basaltic interglacial, intraglacial, and postglacial volcanoes. The lava succession becomes older to the northwest of the area where the zone of young volcanoes gives away to a pile of lavas of pre-Bruhnes epoch age which dip at low angles towards the active zone.This active zone undergoes a change in strike from NE–SW to north–south near latitude 64 °55′N and the volcanoes north of this are smaller in volume than those on the southern extension of the zone. The area of Bruhnes epoch activity dies out above latitude 65 °10′N but much of the area between here and the north coast of Iceland was a line of volcanic activity during the preceding Matuyama epoch.The northern part of the western active zone in Iceland became inactive in late Pleistocene times, and the southern part of the zone is an area of continuing crustal growth. The zone of active volcanism does not terminate against a transform fault and crustal growth is accommodated by deformation of the crustal plate. Lines of crustal growth which subsequently die out can be invoked to explain the anticline and syncline structures in the lava pile and the currently-active Snaefellsnes zone in western Iceland.

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