Ninth International Conference on Permafrost ... - IARC Research

More documents

Recommendations

Info

Potential Subsidence from Thawing of Near-Surface Ground Ice, Outer MackenzieDelta Area, Northwest Territories, CanadaP.D. MorseDepartment of Geography and Environmental Studies, Carleton University, Ottawa, ON, CanadaC.R. BurnDepartment of Geography and Environmental Studies, Carleton University, Ottawa, ON, CanadaS.V. KokeljWater Resources Division, Indian and Northern Affairs Canada, Yellowknife, NT, CanadaIntroductionThe outer Mackenzie Delta area (OMD), on the southeastcoast of the Beaufort Sea, is within the continuous permafrostzone, and typically, permafrost occurs in unconsolidatedsediments with greater than 20% visible ice content in theupper 15–20 m of the ground (Heginbottom et al. 1995).Kendall Island Bird Sanctuary (KIBS), OMD, protects 623km 2 of wetland habitat important to migratory waterfowl andother birds, 60% of which is less than 1.5 m above mean sealevel (Mackay 1963). Research on near-surface permafrost(NSP), defined here as the uppermost meter of permafrost,is necessary because of potential climate change impactson ground conditions, specifically warming of permafrost(Smith et al. 2005) and sea level rise, which is currently 3.5mm/a at Tuktoyaktuk (80 km east of KIBS) (Manson et al.2005). Significant natural gas reserves have been identifiedbeneath KIBS, and there are numerous other explorationleases in the region. Development of these resources wouldrequire construction of production platforms and distributionpipelines. Permafrost degradation in the OMD may lead toinundation and loss of both wildlife habitat and terrain forinfrastructure construction.The objective of this research is to estimate the potentialsubsidence from permafrost degradation at KIBS by (1)determining ground ice content of NSP in various surficialunits; (2) determining the active layer thickness at eachsample location; and (3) calculating the subsidence expectedas the active layer thickens.Surficial Units and Ground IceGround ice contents were assessed in five surficialunits within the two physiographic subdivisions at KIBS(Mackay 1963, Rampton 1988): (1) Tununuk Low Hills atthe southwest, a rolling upland terrain usually less than 50m above mean sea level, interspersed with broad, poorlydrained depressions, covering approximately 30% of thearea; and (2) Big Lake Delta Plain, a flat alluvial wetland,with numerous intersecting channels and lakes that mayflood in spring or with storm surges. Tununuk Low Hills isa mosaic of thermokarst lake beds (TK), gravely sandy hills,ridges and terraces (G), ice-thrust hills and ridges (I), andtill plains (TP). The physiography is due to Wisconsinanadvanceglacial modification of permafrost in Pleistocenemarine and fluvial deposits, post-glacial retreat with NSPaggradation, early Holocene thermokarst activity, andsubsequent development of aggradational ice (Rampton1987, 1988, Burn 1997). Big Lake Delta Plain, whichconsists of fine-grained river deposits (F), was exposedfollowing the Wisconsinan glacial maximum through to themiddle Holocene, and subsequently inundated by sea levelrise or thermokarst lake development. It was then re-exposedbetween 0.5–1.5 ka ago due to fluvio-deltaic infilling andpossible lake drainage (Rampton 1987, Taylor et al. 1996).Ground ice in F developed under saturated conditions withan aggrading surface from sediments deposited annually byspring flooding (Kokelj & Burn 2005).Surficial Units and Ground Ice SamplingThe uppermost 1 m of permafrost was sampled at 72 sitesin KIBS in 2006 and 2007. Cores were collected with a 5cm diameter CRREL drill, and were sectioned into 10 cmintervals. Samples were collected along transects previouslyestablished within TK, G, I, TP, and F surficial units, and ata few other locations. Active layer thickness at each site wasmeasured by probing the late-summer thaw depth (20–27August 2007) (Mackay 1977).Core sections were thawed, re-moulded, and allowed tosettle. A saturated sediment layer with supernatant water ontop was collected in a beaker, and excess-ice content wasestimated with (Kokelj & Burn 2005, Eq. 1):I C= [(W V*1.09)/(S V+(W V*1.09)]*100, (1)where I Cis the excess-ice content (%), W Vis the supernatantvolume, and S Vis the saturated soil volume. The sample wasthen oven dried at 105°C to determine gravimetric moisturecontent (G W).Relation Between Surficial Units andGround IceAll surficial units had high ice content, with higher I Cinthe upper 50 cm of permafrost (Table 1). Lowland NSP (F)was of higher ice content, 34%, than the uplands, on average24%. In the uplands, the highest mean ice content in theuppermost 100 cm of permafrost was in TP, and the lowestwas in G, but G also had the biggest range. In places, theice content in organic-rich deposits at the base of hill slopesexceeded the hilltop ice content by an order of magnitude.215
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tTable 1. Summary statistics for mean I C(%) of the upper 50 and100 cm of permafrost in surficial units of the OMD.Surficial unit Mean Median Min. Max. S.D.F (n = 19)Upper 50 cmUpper 100 cm36.634.136.832.820.018.653.546.39.77.4TK (n = 8)Upper 50 cmUpper 100 cmG (n = 16)Upper 50 cmUpper 100 cmI (n = 9)Upper 50 cmUpper 100 cmTP (n = 10)Upper 50 cmUpper 100 cm26.025.724.820.223.222.632.728.623.326.019.519.224.123.834.128.7Potential Near-Surface Permafrost SubsidenceSubsidence (S) due to a thermal disturbance was estimatedfor each surficial unit using mean upper 50 cm I C(Table1), and active layer thickness increases of 30% and 70%,respectively, after Mackay (1970, Fig. 3):S = {AL I/[(100 - I C)/100]}*{I C/100}, (2)where AL Iis the increase in active layer thickness (cm).Predicted subsidence in the surficial units at KIBS (Table2) is highest in F, yielding 26 cm of water with a 70% increasein active layer thickness. The greatest amount of subsidencein uplands occurs in TP, while subsidence in the remainingunits is nearly uniform.Subsidence is likely underestimated because I Cdoesnot account for the 10% volume of air bubbles commonlyfound in larger ground ice bodies. Additional subsidencewould likely occur from consolidation of thawed soil. Inaddition, the release of water would impact terrain stabilityin unconsolidated sediment, and thermal erosion wouldlikely occur on slopes with modification of drainage patterns(Mackay 1970).Conclusions16.613.41.30.87.87.220.910.538.237.960.039.536.337.847.646.68.08.617.812.38.98.58.411.4*n = number of cores used. Samples from hill slopes are notincluded.1. High ice content (>20% I C) occurred in the uppermost1 m of permafrost in all surficial units in KIBS, and groundice content was highest in the uppermost 50 cm at the baseof the active layer.2. The highest ground ice content was in F, whichaccounts for nearly 60% of the habitat at KIBS.3. An increase of 70% in active layer thickness F, whichis typically less than 1.5 m above mean sea level, woulddecrease the elevation by 26 cm, and increase the chances ofinundation during storm events.Table 2. Thermokarst subsidence estimates based on mean activelayer thickness (AL) and mean upper 50 cm I Cfor surficial unitsof the OMD.Surficial unitF (n = 19; AL = 64)30% increase70% increaseTK (n = 8; AL = 35)30% increase70% increaseG (n = 16; AL = 49)30% increase70% increaseI (n = 9; AL = 48)30% increase70% increaseTP (n = 10; AL = 47)30% increase70% increaseIncrease inthickness ofactive layer(cm)1945102415341434ReferencesTotal depthof thaw(cm)3071143320451844Subsidence(cm)1126Burn, C.R. 1997. Cryostratigraphy, palaeography, andclimate change during the early Holocene warminterval, western Arctic coast, Canada. CanadianJournal of Earth Sciences 34: 912-925.Heginbottom, J.A., Dubreuil, M.A. & Harker, P.A. 1995.Permafrost. In: National Atlas of Canada, 5 th ed.Kokelj, S.V. & Burn C.R. 2005. Near-surface ground icein sediments of the Mackenzie Delta, NorthwestTerritories, Canada. Permafrost and PeriglacialProcesses 16: 291-303.Mackay, J.R. 1963. The Mackenzie Delta area, N.W.T.,Canada. Ottawa: Department of Mines and TechnicalSurveys, Geographical Branch Memoir 8, 202 pp.Mackay, J.R. 1970. Disturbances to the tundra and foresttundra environment of the western Arctic. CanadianGeotechnical Journal 7: 420-432.Manson, G.K., Solomon, S.M., Forbes, D.L., Atkinson, D.E.,& Craymer, M. 2005. Spatial variability of factorsinfluencing coastal change in the Western CanadianArctic. Geo-Marine Letters 25: 138-145.Rampton, V.N. 1987. Surficial Geology, Mackenzie Delta. Map22. In: B.R. Pelletier (ed.), Marine Science Atlas of theBeaufort Sea: Geology and Geophysics. Ottawa: GeologicalSurvey of Canada Miscellaneous Report 40.Rampton, V.N. 1988. Quaternary geology of the TuktoyaktukCoastlands, Northwest Territories. Ottawa: GeologicalSurvey of Canada Memoir 423, 98 pp.Taylor, A.E., Dallimore, S.R. & Judge, A.S. 1996. Late Quaternaryhistory of the Mackenzie–Beaufort region,Arctic Canada, from modelling of permafrost temperatures.2. The Mackenzie Delta – Tuktoyaktuk Coastlands.Canadian Journal of Earth Sciences 33: 62-71.4951141014332149716*n = number of cores used. AL = mean active layer thickness (cm).Samples from hill slopes are not included.216
Page 1:
NICOP 2008 Ninth <
Page 6 and 7:
ContentsPreface ...................
Page 8 and 9:
Mapping and Modeling the Distributi
Page 10 and 11:
Satellite Observations of Frozen Gr
Page 13 and 14:
xiiIce Wedge Thermal Regime in Nort
Page 15 and 16:
xivPermafrost Response to Dynamics
Page 17 and 18:
xvi
Page 19 and 20:
NICOP SponsorsUniversitiesUniversit
Page 22 and 23:
Deep Permafrost Studies at the Lupi
Page 24 and 25:
Effect of Fire on Pond Dynamics in
Page 26 and 27:
Cryological Status of Russian Soils
Page 28 and 29:
Acoustical Surveys of Methane Plume
Page 30 and 31:
Permafrost Delineation Near Fairban
Page 32 and 33:
Preparatory Work for a Permanent Ge
Page 34 and 35:
A Provisional Soil Map of the Trans
Page 36 and 37:
Martian Permafrost Depths from Orbi
Page 38 and 39:
Time Series Analyses of Active Micr
Page 40 and 41:
Impact of Permafrost Degradation on
Page 42 and 43:
DC Resistivity Soundings Across a P
Page 44 and 45:
Modeling Thermal and Moisture Regim
Page 46 and 47:
A Provisional Permafrost Map of the
Page 48 and 49:
Alpine Permafrost Distribution at M
Page 50 and 51:
Cryogenic Formations of the Caucasu
Page 52 and 53:
Modeling Potential Climatic Change
Page 54 and 55:
A Hypothesis: A Condition of Growth
Page 56 and 57:
Modeled Continual Surface Water Sto
Page 58 and 59:
Freeze/Thaw Properties of Tundra So
Page 60 and 61:
Discontinuous Permafrost Distributi
Page 62 and 63:
Thermal Regime Within an Arctic Was
Page 64 and 65:
Seasonal and Interannual Variabilit
Page 66 and 67:
Twelve-Year Thaw Progression Data f
Page 68 and 69:
Continued Permafrost Warming in Nor
Page 70 and 71:
Landsliding Following Forest Fire o
Page 72 and 73:
A Permafrost Model Incorporating Dy
Page 74 and 75:
Seasonal Sources of Soil Respiratio
Page 76 and 77:
Greenland Permafrost Temperature Si
Page 78 and 79:
The Importance of Snow Cover Evolut
Page 80 and 81:
The Account of Long-Term Air Temper
Page 82 and 83:
The Combined Isotopic Analysis of L
Page 84 and 85:
Adaptating and Managing Nunavik’s
Page 86 and 87:
Human Experience of Cryospheric Cha
Page 88 and 89:
HiRISE Observations of Fractured Mo
Page 90 and 91:
A Soil Freeze-Thaw Model Through th
Page 92 and 93:
Mapping and Modeling the Distributi
Page 94 and 95:
First Results of Ground Surface Tem
Page 96 and 97:
Historical Changes in the Seasonall
Page 98 and 99:
Rock Glaciers in the Kåfjord Area,
Page 100 and 101:
Snowpack Evolution on Permafrost, N
Page 102 and 103:
Climate Change in Permafrost Region
Page 104 and 105:
Maximizing Construction Season in a
Page 106 and 107:
Pleistocene Sand-Wedge, Composite-W
Page 109 and 110:
Ni n t h In t e r n at i o n a l Co
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Ni N t h iN t e r N at i o N a l Co
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186: Ni n t h In t e r n at i o n a l Co
Page 217 and 218: Ni N t h iN t e r N at i o N a l Co
Page 235: Ni n t h In t e r n at i o n a l Co
Page 253: Ni n t h In t e r n at i o n a l Co
Page 287 and 288:
Page 289 and 290:
Page 291 and 292:
Page 293 and 294:
Page 295 and 296:
Page 297 and 298:
Page 299 and 300:
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317 and 318:
Page 319 and 320:
Page 321 and 322:
Page 323 and 324:
Page 325 and 326:
Page 327 and 328:
Page 329 and 330:
Page 331 and 332:
Page 333 and 334:
Page 335 and 336:
Page 337 and 338:
Page 339 and 340:
Page 341 and 342:
Page 343 and 344:
Page 345 and 346:
Page 347 and 348:
Page 349 and 350:
Page 351 and 352:
Page 353 and 354:
Page 355 and 356:
Page 357 and 358:
Page 359 and 360:
Page 361 and 362:
Page 363 and 364:
Page 365 and 366:
Page 367 and 368:
Page 369 and 370:
Page 371 and 372:
Page 373 and 374:
Page 375 and 376:
Page 377 and 378:
Page 379 and 380:
Page 381 and 382:
Page 383 and 384:
Page 385 and 386:
Page 387 and 388:
Page 389 and 390:
Page 391 and 392:
370Huang, B. 339Hugelius, G. 105, 1
Page 393:
372
show all

Ninth International Conference on Permafrost ... - IARC Research

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?