Glacsweb project Learning and tuning Results Environmental Sensor Network challenges

1. Using sensor networks to explore the subglacial environmentJane K. HartGeography and EnvironmentUniversity of Southampton

2. Glacsweb project • Learning and tuning • Results • Environmental Sensor Network challenges Design build Deploy learn

3. Glacsweb aims • study glacier dynamics • sensor network research • produce generic components and expertise useful in other environments

4. Engineering Challenges • Probes must be small and reliable • Robust Communications • Adaptive behaviour • Low power for longevity • Live system for experiments and data access

5. Glacier movement creep Sliding/stick-slip motion Subglacial deformation

6. Subglacial data Supraglacial data GLACSWEB: Understand the role of the subglacial bed in glacier dynamics

7. Skalafellsjökull Briksdalsbreen

8. Site locations • Resting on deformable sediments • GSM phone & local broadband • Good access! • Briksdalsbreen active advance (and retreat!) • Skalafellsjökull potential for up to 300m deep analysis. Briksdalsbreen Skalafellsjökull

9. Field site 03 (65m) Field sites 04, 05 & 06(60m),(50m)&(40m)

10. Briksdalsbreen 2001 2007

11. Skalafellsjökull, Iceland, 2008-10 (70m) 2011 (120m)

12. System Overview cloud Base Station WiFi Ref station WiFi Glacier Sensor network server Sediment PC Southampton Probes geophones

13. Probes • Polyester case • 433MHz, 173MHz, 151MHz Radio • Sensors: Temp, Press, Strain, Resistance, Tilt, Volts • 30 installed in 2003-2008 2004/5 2008 2011 2006

14. CAD diagrams of probe by Mark Long ECS Mechanical Workshop

15. Probe pressure tests in Oceanography

16. Sensor data buffering Probes store their data until they manage a connection Base Station Ice D D Sediment

17. Ad-hoc network gains Probes “talk” via best route Base Station Ice Sediment

18. Base Station Measure Weather, box tilt, battery Volts Radio links gateway and probes DGPS rover Ubuntu Linux ARM CPU wind & solar power geophones Uses 1.4W when on, negligible in Sleep mode

19. Base station

20. Base station architecture Switching sensor interfaces Gumstix runs Linux MSP430

21. Reference Station • Mains power in summer • Mobile Phone GPRS • Records dGPS data • sends data to farm in valley 15km away

22. Live data available on the web

24. Deployment

25. Results • 2003/2004 • 14 probe days • 2004/2005 • 859 probe days • 2005/2006 • 1255 probe days • 2008/10 • 1205 probe days

26. Ground Penetrating Radar • Probes • Borehole camera • Hot water drilling • GPS • In situ sampling

27. Ice/Till Interface

29. Probes in a till–based borehole

30. Unique results • High water pressure events • Quantification of tilt • Grain behaviour, rheology and water content • Till temperatures • Stick-slip events

31. Water pressure Briksdalsbreen Summer Autumn Spring Winter Skalafellsjökull Water pressure high throughout the year Series of short term events

32. Briksdalsbreen • Lake • Coarse grained till Skalafellsjökull • Steep bedrock • Fine grained till

33. Probe tilt

34. Briksdalsbreen 3.5° / week 2° / week 0.6° / week 4.2 ° / week y direction

35. Rotation • Two models for clast behaviour in deforming layer • Active rotation (Jeffrey, 1923; Glen et al., 1957; Hart, 1994) • Stable position (March, 1932; Hooyer & Iverson, 2000)

36. Skalafellsjökull • When air temp rise above 2.5o • wp fall, tilt changes • This generates high melt-water, allows glacier to ‘slip’ • Afterwards, wp slowly builds up ‘stick’

37. Grain behaviour, rheology and water content High water pressure and water content Briksdalsbreen

38. High water pressure/weak till • Grain arrangement as a result of shearing. • Linear viscous behaviour after a critical yield stress of 35 kPa • Till Viscosity (Pa s) 3.6 -7.3 x109 • Till discharge per 1m3 section per year (m3 a-1) 1.3-5.6

39. Briksdalsbreen

40. Low water content/strong till • Stick-slip events directly transmitted via the grain structure through a relatively strong till

41. Till Temperatures High water pressures Low till temperatures MELTWATER

42. Till Temperatures Low and Intermediate water pressure High till temperatures

43. ‘Flash’ temperatures • This temperature increases can be accounted for using the ‘flash’ temperature model (Bestmann et al., 2006; Archard, 1958)

44. Conclusions • Designed, tested and deployed different probe versions • Experience in the problems of ESN communications, especially in a glacial environment • Investigate subglacial processes and stick-slip motion, e.g. water pressure, clast rotation and till temperature.

45. Challenges for Environmental Sensor Networks • Power Management • Standardisation • Low cost • Integrating and analysing large data sets • Development of new sensors(particularly) biosensors, sensor proxies and envinodes

46. Evolution from logging to ESN • Large Nodes to ‘smart dust’

47. 2003 2004 2008 2006 2006 2005

48. Probe architecture

49. Base Station Architecture

50. Probes 3.6 V Lithium Thionyl Chloride Cells 6AH worth of energy 4µW in sleep mode 370mW in receive mode 470mW in transmit mode Life aprox. 10 years!! Base Station Powered with lead-acid gel batteries 96AH worth of energy 120mW in Bitsy’ssleep mode 50mW in weather station sleep mode Powered up daily for a maximum of 15 min Approximate daily consumption 5WH Estimated battery life is 230 days Power Consumption • Base 2008 • 36Ah • 25µW • maximum of 3 min • Runs until damaged