1 / 33

An autonomous multi-sensor probe for taking measurements under glaciers

An autonomous multi-sensor probe for taking measurements under glaciers. Dr Kirk Martinez & Dr Jane K. Hart Electronics and Computer Science & Dept. of Geography. Advisors. Prof. Harvey Rutt Dr Joe Stefanov Workshop: Ken Frampton PIC: Tim Forcer.

Download Presentation

An autonomous multi-sensor probe for taking measurements under glaciers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. An autonomous multi-sensor probe for taking measurements under glaciers Dr Kirk Martinez & Dr Jane K. Hart Electronics and Computer Science & Dept. of Geography

  2. Advisors • Prof. Harvey Rutt • Dr Joe Stefanov • Workshop: Ken Frampton • PIC: Tim Forcer

  3. A Subglacial ProbeAn autonomous multi-sensor probe for taking measurements under glaciers • Introduction • Current Research Methods • Subglacial Probe • Site details • Radar details of ice/sediment • Probe details • Revised Timetable and Conclusion

  4. Introduction • Current day ‘Global Warming’ represents one of major changes to our social and environmental well being • One key element of climate change is the response of glaciers - sea level change, and changes to the thermohaline circulation in the North Atlantic • Vital to understand behaviour of the subglacial bed

  5. Subglacial Deformation • Movement in sediment can comprise 90% of glacier motion • Requires high pore water pressures

  6. Current research methods • Geophysical techniques (seismic and radar) are mostly static and of low resolution • In situ process studies

  7. Ground Penetrating Radar Ground Penetrating Radar, example from Breidamerkurjokull

  8. In situ process studies • Sediment strength (ploughmeter) • Sediment deformation (tiltmeter) • Sediment velocity (dragspools)

  9. SedimentStrength Ploughmeter

  10. Ploughmeter Variations in sediment strength - typical viscous model for sediment behaviour Example from Vestari- Hagafellsjokull, Iceland

  11. Amount of deformation Tilt cells

  12. Tiltmeter -8cm Variations in tilt -15cm Example from Vestari- Hagafellsjokull, Iceland

  13. Amount of deformation/sliding Drag Spools

  14. Summary • Current techniques useful, but because they are tethered they do not behave in a ‘natural’ manner

  15. Subglacial Probe • Smart sensor “pebbles” tracked by radio

  16. Site details • Briksdalsbreen in Norway • Advanced 400m since 1988 over silty clay (lake bed) • Average July surface velocity 1996-2000 was 0.33 m/day - basal velocity normally 70% of surface so predicted velocity 0.23 m/day • Expected deforming bed thickness: 0.2 - 0. 3m • Expected ice thickness at drill site: 100m

  17. Properties of ice/sediment • dielectric constant of ice: •  ≈ 3.17  ≈ 0.003 • frozen sediments  ≈ 3.8 • dry sediments  ≈ 4.4 • DC conductivity ≈ 10-5 to 10-6 S m-1

  18. Probe Details • Sediment strength • Sediment deformation • Sediment velocity • Sediment temperature • Holes will be drilled by hot water drill • Probes will be inserted at 5 sites

  19. Sediment Strength • Stress gauges in probe ICE Probe SEDIMENT

  20. Sediment Deformation (rotation) • 10 degree accuracy sufficient • 2 tilt cells ICE Probe SEDIMENT

  21. Velocity(position) • 10-50cm accuracy in position • Transponder ICE Probe SEDIMENT

  22. Temperature and Pressure • 1 – 2 C accuracy sufficient • Thermistor and Pressure sensor ICE Probe SEDIMENT

  23. Basic Design Base Station DGPS Ground station Ice Sediment

  24. Movement in a year Base Station 13m DGPS Ground station Ice 10m 7m 3m Sediment

  25. Probes • Hard oval case probably potting-filled • PIC microprocessor & RAM • Data Transmitter & radar transponder • A/D and amplifiers • Powerful batteries • Sensors: tilt, temp. pressure, … • May measure hourly, transmit and sleep

  26. Radio calculations • Velocity in ice ≈ 0.16 m/ns • 1.8GHz wavelength = 0.167 m •  = 4  Im(√) /  = 0.063 m-1 • Attenuation = e -  L For L = 100m Attenuation = 27 dBm ie within range

  27. Probe Case • Made of strong milled material • two halves • Use join area for antennae • Padded interior

  28. Base Station • Computer with larger storage • Large power supply (lead-acid gell plus Solar top-up) • DGPS for position relative to ground station • Receiver for Probe data • GSM/Satellite phone connection home • Position radar antennas to track probes

  29. Ground Station • DGPS base station to locate base station on glacier

  30. Power estimate • 400mA for 2s every hour is 2AH/year • Lithium AA batteries reach 2-3 AH • Estimate 6 batteries for 7V approx. • Can reduce on/off ratio if necessary

  31. Testing • Mechanical testing of case • Telemetry testing • Sensor testing/calibration • Accelerated power drain testing at -5oC • Traditional instruments will also be inserted in glacier for comparison

  32. Timetable

  33. Conclusions • Probe allows: • less invasive monitoring of the subglacial • more natural mimicking of clast behaviour • Technical solution is feasible • This will be the first instrument of its kind for earth observations

More Related