Thaw Tube Temp. Loggers

Transcription

1 Thaw Tube Temp. Loggers clear inner tube radiation shield (6 plate, 12 cm) thermistor (1.5 m high) grill supporting heave sleeve heave sleeve with scriber ground surface frost table markers water guys ice PVC pipe outer tube relief holes expansion chamber access fitting data logger (air temperature) silicon fluid steel pipe ground surface data logger (ground temperature) G S

2 68 N Mackenzie Valley CALM Sites 70 N 137 W 132 Low Arctic 137 W 125 W 70 N N Subarctic High 0 Kilometres 100 Low Subartic 65 N High Subhumid Boreal G S Subhumid Mid-Boreal 60 N 125 W 116 W

3

4

5 Statement of Work Outer tube: (see sketch) -supply materials as required. -cut pipe to 4 meter lengths -weld ¾ P.V.C. caps on one end of pipe (must be water tight) -provide loose caps for other end Inner tube: (see sketch) -supply materials as required, clear tubing, including top ring, must be tough, Lexan or fully equivalent. -trim ¾ x 5 / 8 " clear Lexan tube to 2.5 meters -fit and bond 1 cm. collar of 1" x ¾ Lexan on one end -insert and position # 0 rubber stopper 20 cm. from other end of tube. -fit and bond 2 cm. long plug of 5 / 8 " Lexan rod in end of tube below stopper -drill two 4 mm. relief holes through tube just above plug Packing and delivery: -combine inner and outer tubes with loose caps taped on and pack for shipment -deliver to. Please quote on cost for each component (outer and inner tube assemblies). Order will be of each. Contact: Mark Nixon Geological Survey of Canada Booth Street Ottawa, Ontario K1A 0E8 phone fax mnixon@nrcan.gc.ca

6

7

8 Thaw Tube Installation: We install our tubes, anchored in permafrost at least twice the thickness of the expected active layer, using a low pressure, low volume water jet from a small pump down a small diameter (~3/4") string of pipe. The pump should have a discharge of at least 150 liters per minute but low pressure that allows use of light weight garden hose joined to the wash pipe via a swivel and valve for adding lengths. A very small pool or even a flooded frost wedge trough is usually sufficient water to wash a few meters. We protect the ground surface with a plastic sheet perforated by a short piece of plastic surface casing, diverting and collecting washed material on the sheet. When the desired depth has been reached the long access tube, with a couple of hose clamps tightened below permafrost depths as anti heave surfaces, is installed and the collected material is put back down the annulus around the tube. If necessary, the surface is carefully washed to uncover the original vegetation. Deionized water is put in the observation tube up to a level about 25 cm above the expected bottom of the active layer. Keeping the water below the ground surface reduces problems of locking of the top of a freezing column and expansion downward, potentially moving the markers. For a 4 meter access tube containing a 2.5 meter observation tube, about 2 liter of silicon oil, 50 centistoke viscosity, is poured into the access tube to stop frost buildup and convection (in these small diameter tubes convection is not expected to be a problem and several test tubes that have been without silicon for up to 5 years show no sign of sticking due to frost buildup). The access tube between the ground surface and 20 cm. above the scriber is painted with an easily scratched quick drying spray paint, white is good if tube is exposed to radiant heating. The grill and scriber sleeve (grill is a stiff wire mesh about 3 cm square, sleeve is a 10 cm length of steel pipe with a piece of band saw or hack saw blade with a V notch cut out to produce 2 points clamped to the pipe for a scriber) is placed over the outer tube which is closed with a slip cap and taped to prevent water from snow melt or flooding from flowing into the tubes. Normally the water column does not freeze back quickly so if the site cannot be visited late in the installation season, the first marker bead cannot be installed before the following season. This type of installation has shown good resistance to heaving and site disturbance is minimal. Surface vegetation often recovers fully within a couple of years. Only in two of over 70 installations, has serious subsidence of a site been observed. All of the equipment necessary for an installation can be carried by two people over a distances of a few kilometers, again reducing the impact on natural situations. (This is an off the cuff description of our procedure) F. Mark Nixon Terrain Sciences Division / Division de la science des terrains Geological Survey of Canada / Commission géologique du Canada rue Booth Street Ottawa (Ontario) K1A 0E8 ph. / téléphone (613) fax / télécopieur (613) mnixon@nrcan-rncan.gc.ca ou index_fr.htm

9 THAW TUBE OBSERVATIONS RATIONAL: To monitor maximum annual depth of thaw and maximum heave / subsidence of ground surface at sites near other monitoring stations and in different environmental situations. LOCATIONS: FREQUENCY: DURATION: UNITS: PRECISION: REFERENCE: OBSERVATIONS: EQUIPMENT: Your site(s) Annually or on opportunity basis. As long as possible, decades Metric, centimeters. +_ 1 mm. Top of inner tube (see tube diagram). Snow depth and character (dense, light, crusty, hoar, etc.) Frost probe (push thin probe to frozen soil and measure depth) Scriber height (see observation diagram). Tube height (see observation diagram). Depth to water surface (see diagrams). Depth to ice surface(s) (see observation diagram) Depth to bead(s) (see observation diagram). Distance stopper pushed from mark (see observation diagram) Distance stopper to plug (see observation diagram) Condition of tube bottom Disturbance Other observations Metric tape measure Frost probe Wipers (for silicone) Meter stick (snow depth) Marker beads Spray paint Plastic sheet Vinyl tape

10 PROCEDURE: in winter: in summer: -Take three or four snow depths within 1 meter of tube. If snow is covering the tube do not disturb; skip further observations. -Describe snow character such as dense, light, crusty, hoar, etc.. -Take three frost probe sounding within 50 cm. of tube on similar level. each visit: -Note any disturbances, eg. animal gnawing, track, etc. -Assure heave/subsidence sleeve is resting on grill (see tube diagram). -Measure distance of scribes above and below the reference mark and the current position of the scriber point relative to this mark. -Remove cap. Assure inner tube collar is in contact with outer tube top. -Measure from top to scriber position (scriber height on observation diagram). -Measure height to metal grill, upper wires, at mid point if tilted. If grill covered by snow, measure to top of heave/ subsidence sleeve (tube diagram). -Withdraw tube and measure depth from top to water and ice surface(s) (during freeze back in fall there may be an upper ice surface above water from downward freezing as well as a lower surface rising as freezing progresses from below). Refer to observation diagram. Avoid keeping tube out too long in warm air temperature as ice column may loosen and float to top. -Measure depth to bead(s) (observation diagram). -Measure from stopper bottom to top of plug (observation diagram). Note condition of bottom of tube eg. stopper pushed to bottom, plug protruding. -Add new coloured marker bead (for current year before maximum thaw), assuring bead reaches ice surface. -Replace inner tube and cap, tapeing cap to tube. -Repaint outer tube where scratched, protecting ground surface and vegetation with plastic sheet or garbage bag. -When paint is dry, rotate scriber to produce new horizontal reference scribe. - Other general observations; photos. F. Mark Nixon Terrain Sciences Division / Division de la science des terrains Geological Survey of Canada / Commission géologique du Canada rue Booth Street Ottawa (Ontario) K1A 0E8 ph. / téléphone (613) fax / télécopieur (613)

11

12 LOCATION: DATE: SITE #: TUBE HEIGHT: HEAVE/SUB: Max. Min. Current DEPTH TO WATER: DEPTHS TO FROST TABLE: obs1 obs2 obs3 obs4 SCRIBER HEIGHT: DEPTH TO ICE SURFACE(S): DEPTH TO BEAD(S): 1st 2nd 3rd other CONDITION OF TUBE BOTTOM: stpr to plg pushed DISTURBANCE: GENERAL COMMENTS: LOCATION: DATE: SITE #: TUBE HEIGHT: HEAVE/SUB: Max. Min. Current DEPTH TO WATER: DEPTHS TO FROST TABLE: obs1 obs2 obs3 obs4 SCRIBER HEIGHT: DEPTH TO ICE SURFACE(S): DEPTH TO BEAD(S): 1st 2nd 3rd other CONDITION OF TUBE BOTTOM: stpr to plg pushed DISTURBANCE: GENERAL COMMENTS: LOCATION: DATE: SITE #: TUBE HEIGHT: HEAVE/SUB: Max. Min. Current DEPTH TO WATER: DEPTHS TO FROST TABLE: obs1 obs2 obs3 obs4 SCRIBER HEIGHT: DEPTH TO ICE SURFACE(S): DEPTH TO BEAD(S): 1st 2nd 3rd other CONDITION OF TUBE BOTTOM: stpr to plg pushed DISTURBANCE: GENERAL COMMENTS:

13 LITERATURE Banner, J.A. and R.O. van Everdingen. Frost Gauges and Freezing Gauges, National Hydrology Research Institute, Paper No. 3, Environment Canada, Ottawa, 1979, 18 p. Mackay, J. R. "A frost tube for the determination of freezing in the active layer above permafrost," Canadian Geotechnical Journal, Vol. 10, no. 3, 1973, pp Nixon, F. M. and A. E. Taylor. "Active layer monitoring in natural environments, Mackenzie Valley, Northwest Territories," Geological Survey of Canada, Current Research, Vol B, 1994, pp Nixon, F.M., Taylor, A.E., Allen, V.S. and Wright, F. Active layer monitoring in natural environments, lower Mackenzie Valley, Northwest Territories, in Geological Survey of Canada, Current Research, Vol B, 1995, pp Nixon, F. M. and A. E. Taylor. "Regional active layer monitoring across the sporadic, discontinuous and continuous permafrost zones, Mackenzie Valley, northwestern Canada," in: A. G. Lewkowicz and M. Allard, eds., Proceedings of the Seventh International Conference on Permafrost, Québec: Centre d'études nordiques, Université Laval, 1998, pp Nixon, F.M. Thaw-depth monitoring in: L.D. Dyke and G.R. Brooks, eds., The Physical Environment of the Mackenzie Valley, Northwest Territories: a Base Line for the Assessment of Environmental Change, Geological Survey of Canada, Bulletin 547, 2000, pp Rickard, W. and J. Brown. "The performance of a frost-tube for the determination of soil freezing and thawing depths," Soil Science, Vol. 113, no. 2, 1972, pp Smith SL, Burgess MM, Nixon FM Response of active-layer and permafrost temperatures to warming during 1998 in the Mackenzie Delta, Northwest Territories and at Canadian Forces Station Alert and Baker Lake, Nunavut, In Current Research 2001-E5: Geological Survey of Canada: Ottawa; (8 pp). Wolfe, S. A., E. Kotler, and F. M. Nixon. "Recent warming impacts in the Mackenzie Delta, Northwest Territories, and northern Yukon Territory coastal areas," Geological Survey of Canada, Current Research, Vol. 2000(B1), Nixon, M., C. Tarnocai and L. Kutny. Long-term active layer monitoring: Mackenzie Valley, northwest Canada ; in M. Philips, S. Springman and L.U. Arenson (eds.), Permafrost, Vol. 2, A.A. Balkema Publishers, Swets & Zeitlinger, Lisse, The Netherlands, 2003, pp

14 Charles Tarnocai, F. Mark Nixon, Les Kutny. Circumpolar-Active-Layer-Monitoring (CALM) sites in the Mackenzie Valley, northwestern Canada ; Permafrost and Periglacial Processes, Volume 15, Number 2, 2004, pp