Geological Survey of Denmark and Greenland Bulletin 33, 2015, 61-64 61 Unique applied glaciology challenges of proglacial mining William Colgan, Henrik Højmark Thomsen and Michele Citterio Th e glaciology group at the Geological Survey of Denmark and Greenland (GEUS) has a tradition of applied glaciology consulting for hydropower projects in Greenland (Weidick & Th omsen 1982; Braithwaite & Olesen 1988; Ahlstrøm et al. 2008). Th is includes assessments for the hydropower plants now operating at Ilulissat and Nuuk (Braithwaite & Th omsen 1989; Th omsen et al. 1989; 1993), as well as the outburst potential of ice-dammed lakes such as Qorlortorsu- up Tasia (Mayer & Schuler 2005). Several factors, including long term increases in global resource demand, increasing air temperatures and glacier retreat due to climate change, and improved mining and prospecting techniques may now im- prove the economic feasibility of mining in Greenland (Col- gan & Arenson 2013). Given that over 80% of Greenland is ice-covered, mining projects in Greenland oft en occur in ‘proglacial’ settings, meaning adjacent to, or close to, an ice margin. Th e Isukasia, Kvanefj eld, Maarmorilik and Malmb- jerg prospects exemplify resource development in proglacial settings in Greenland. Th e glaciology group at GEUS has a growing interest in the applied glaciology aspects of proglacial mining projects, and was recently engaged to assess ice fl ow, meltwater run- off , and supraglacial road access for the Malmbjerg prospect in East Greenland (Citterio et al. 2009), as well as provide expert commentary on the Kumtor Mine in Kyrgyzstan (Satke & Galdini 2014). Approximately 3.5 km2 of glacier overburden was removed at the Kumtor Mine between 1998 and 2014, creating the world’s largest open ice pit, in order to recover subglacial ore (Fig. 1). Th e open ice pit approved in 2013 for the Isukasia (or ‘Isua’) mine would be several times larger (Fig. 2). Applied glaciology addresses a number of unique geotechnical challenges associated with proglacial mining projects, here, we briefl y review four: supraglacial runoff , subglacial water fl ow, ice movement and supraglacial access roads. 2 km 78°16´E 41°55´N 41°50´N Mine area (1998) Ice margin (1977) Mine area (2014) Ice margin (1977) 78°9.5´E Fig. 1. Kumtor Mine, Kyrgyzstan. Historic ice margins and contemporary mine areas overlaid on 1998 (left) and 2014 (right) Landsat images. © 2015 GEUS. Geological Survey of Denmark and Greenland Bulletin 33, 61–64. Open access: www.geus.dk/publications/bull 6262 Unique Challenges It can be diffi cult to quantify and manage supraglacial melt- water runoff near the ice sheet margin. In southern Green- land, the annual ice melt (or ‘ablation’) can exceed 8 m water equivalent per unit area per melt season (Fausto et al. 2012). By comparison, the record annual rainfall on Earth is c. 12 m water equivalent in Meghalaya, India. In Greenland, howev- er, the annual meltwater runoff is concentrated during a rela- tively brief summer melt season. During the melt season, wa- ter-saturated snowpacks are susceptible to slushfl ows, which can damage infrastructure both on, and adjacent to, glaciers (Smart et al. 2000). While surface mass-balance parameters generated by regional climate models can be calibrated with in situ data to assess the magnitude and spatial distribution of meltwater production (van As et al. 2014), estimates of the runoff that drains to any given proglacial site are very sen- sitive to the delineation of the supraglacial catchment areas (Arenson & Colgan 2015). Uncertainty in the catchment de- lineation over the relatively fl at ice sheet can easily contrib- ute to 50% uncertainty in runoff (Rennermalm et al. 2013). Recent work has also demonstrated that supraglacial streams regularly breach local topographic divides, making it diffi - cult to justify the application of strictly elevation-dependent terrestrial water routing algorithms to the ice sheet (Smith et al. 2015). Manual delineation of supraglacial catchments from high-resolution imagery is a time-consuming, but more accurate, alternative (Th omsen et al. 1989). It is also important to assess the subglacial water fl ow reaching any given proglacial site, as the vast majority of meltwater ‘runoff ’ produced on the surface of the ice sheet enters the en- and subglacial networks prior to discharge at the ice sheet margin (Smith et al. 2015). Analogous to ter- restrial groundwater fl ow, the en- and subglacial hydrologic networks of the ice sheet have traditionally been conceptual- ised as saturated porous fl ow, whereby the en- and subglacial water fl ow is governed by hydraulic potentiometric surfaces that can be predicted using ice geometry (Lewis & Smith 2009). Recent observations, however, indicate that chan- nelised subglacial drainage and non-trivial head fl uctua- tions extend tens of kilometres inland beneath the ice sheet (Chandler et al. 2013). Unlike groundwater fl ow through rock or sediment, the transmissivity of channelised fl ow in glacier ice can change rapidly, within hours or days, in re- sponse to both frictional melting along conduit walls and opening or closing due to viscous creep. As supraglacial lakes ice margin (c. 2010) proposed pit area movement (m/a) 10 100 Green- land 3 km49°40´W49°50´ 65°10´N Ice margin c. 2010 Proposed pit area Movement (m/a) 10 100 Fig. 2. The potential ‘Isua’ mine, Greenland, approved in 2013. Contem- porary ice margins, proposed approximate pit area, and winter 2005/06 ice surface velocity vectors (Joughin et al. 2010). The background is a 2014 Landsat image. 200 100 0 Operational year 0.0 Distance inland (km) El ev at io n (m ) 0 0.5 1 1.5 2 2.5 200 100 0 60 50 40 30 20 10 0 Operational year 10.0 A B Distance inland (km) El ev at io n (m ) 0 0.5 1 1.5 2 2.5 Ic e ve lo ci ty (m /y ) Fig. 3. Cross-sections of a glacier tongue with ice velocities (m/year). A: The glacier tongue has an undisturbed profile in operational year 0. B: After 10 years of excavation the ice wall has a gradient of 33%. The ice velocities have increased from 10–20 m/year to >60 m/year at the crown. The complete ani- mation is available at www.williamcolgan.net/som/CRENG113 (Colgan 2014). 63 can catastrophically release large volumes of meltwater (c. 109 l) into the subglacial network via crevasse hydrofracture (Liang et al. 2012), there is a strong impetus to understand the preferential subglacial drainage routes in the vicinity of any given proglacial site. Glacier ice movement can be so imperceptible over shorter time scales (hours to days) that glacier ice is commonly, but not strictly correctly, characterised as a solid. Over longer time scales (years to decades), the true non-Newtonian fl uid character and appreciable movement of ice becomes evident (Colgan & Arenson 2013). Th e creep of glacier ice under gravitational stress can cause operational diffi culties due to ice movement beneath or against infrastructure, such as waste dumps and processing facilities (Citterio et al. 2009). An exceptionally challenging task is to forecast ice fl ow into open ice pit excavations. Due to the non-linear dependency of ice velocity on both ice thickness and surface gradient, the excavation of an open ice pit increases subsequent ice fl ow into the open ice pit (Colgan 2014). Perturbation of a natu- ral glacier profi le into an artifi cial ice wall with a gradient of 33% can increase crown velocities by an factor of fi ve (Fig. 3). Open ice pits therefore require continuous excavation of substantial ice volumes to maintain pit geometry. Over the lifecycle of a proglacial mine, this may require excavating several times the ice volume of an open ice pit itself. Unlike conventional open pits in hard rock, the relative rapidity with which ice benches deform means that even temporary stoppages in ice excavation can adversely aff ect ice pit shape and fl ow (Els 2012). Th e establishment and maintenance of supraglacial access roads are oft en critical elements of proglacial mining projects (Citterio et al. 2009). Traversing the relatively subdued to- pography of a glacier can be preferable to traversing the rela- tively severe topography of proglacial areas with abundant rivers and erratics (Fig. 4). In addition to potential crevasse hazards, supraglacial access roads can be compromised due to horizontal and vertical ice movement and diff erential surface ablation. While horizontal ice movement is readily observable by satellite (Fig. 2), vertical ice movement can be heterogene- ous over short distances, where compressive and extensional fl ow result in opposing vertical movements via thrust- and slip-faulting along ice fractures (Nye 1952). It is desirable to establish a metre-scale aggregate, supraglacial road bed fol- lowed by continual grading in order to minimise the infl u- ence of heterogeneous vertical ice movements. Th is also im- proves road stability by keeping the ice beneath a road frozen throughout the year. However, active suppression of ablation beneath a supraglacial road results in perching of a road above the surrounding glacier surface (Davis 1967). Perching and consequent shoulder slumping hazards make roads that trav- erse glaciers even more sensitive to thermodynamic condi- tions than roads that traverse permafrost areas. Additionally, as a consequence of glacier margin retreat, which can exceed 10 m per year, approach ramps at the transition from non- to ice-covered terrain require persistent maintenance on a week- ly basis during the melt season (Davis 1967). Summary Climate change will further exacerbate the unique applied glaciological challenges associated with proglacial mining described above. Rising atmospheric temperatures are ex- pected to increase the meltwater runoff from the ice sheet by a factor of fi ve by the end of the century (Fettweis et al. 2013). Th e probability of individual catastrophic supragla- cial lake drainage events into the subglacial system is pro- portional to this summer melt intensity (Liang et al. 2012). As ice rheology, i.e., the relation between stress and strain, is highly temperature dependent, the tremendous latent energy of meltwater can heat the ice and accelerate ice deformation (Phillips et al. 2013). Th e challenge of maintaining supragla- cial road access increases with the length of the melt season Fig. 4. The potential Kerr-Sulphurets-Mitchell mine in Canada, approved in 2014. Proposed approximate mine area, contemporary ice margins and supraglacial access road. The background is a 2014 Landsat image. The analogous features of the nearby Brucejack prospect are also shown. Brucejack Kerr-Sulphurets-Mitchell Ice margin (2012) 56°24´ 56°32´ 130°18´ 5 km130°4´E 56°16´ 56°24´N 6464 Authors’ address Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: wic@geus.dk and surface ablation (Davis 1967). Finally, with glaciers serv- ing as highly visible indicators of climate change, proglacial mining projects oft en face exceptional public opposition in comparison to conventional hard rock mining projects (e.g. Satke & Galdini 2014). As described in this report, the GEUS glaciology group has both a history of providing commercial services for proglacial projects, and a familiarity with the unique chal- lenges confronting future proglacial projects. Th e glaciology group has carried out extensive research and monitoring programmes in Greenland for more than sixty years. During this time, the glaciology group has developed a broad suite of glaciology-specifi c instrumentation, including autonomous climate stations that are capable of reporting numerous pa- rameters via satellite link at hourly time intervals. Th e ongo- ing Programme for Monitoring of the Greenland Ice Sheet (PROMICE), generates a large amount of climatology and glaciology data, as well as ensures a glaciology group presence for survey and maintenance operations around the ice sheet perimeter. When synergistic, the glaciology group partners with Asiaq (Greenland Survey) on joint projects. In addition to serving as an advisory institute to the Danish Ministry of Climate and Energy, GEUS also serves as a contractually appointed advisory institute to the Greenland Ministry of Mineral Resources. References Ahlstrøm, A., Mottram, R., Nielsen, C., Reeh, N. & Andersen, S. 2008: Evaluation of the future hydropower potential at Paakitsoq, Ilulissat, W. Greenland. Danmarks og Grønlands Geologiske Undersøgelse Rap- port 2008/37, 50 pp. Arenson, L. and Colgan, W. 2015: Water management challenges associ- ated with mining projects in Greenland, 533–543. Proceedings of Mine Water Solutions in Extreme Environments 2015. Vancouver, Canada. Braithwaite, R.J. & Olesen, O. 1988: Eff ect of glaciers on annual run-off , John Dahl Land, South Greenland. Journal of Glaciology 34, 200–207. Braithwaite, R.J. & Th omsen, H.H. 1989: Simulation of run-off from the Greenland ice sheet for planning hydro-electric power, Ilulissat/Jakob- shavn, West Greenland. Annals of Glaciology 13, 12–15. Chandler, D.M. et al. 2013: Evolution of the subglacial drainage system beneath the Greenland ice sheet revealed by tracers. Nature Geoscience 6, 195–198. Citterio, M., Mottram, R., Larsen S.H. & Ahlstrøm, A. 2009: Glaciologi- cal investigations at the Malmbjerg mining prospect, central East Green- land. Geological Survey of Denmark and Greenland Bulletin 17, 73–76. Colgan, W. 2014: Considering the ice excavation required to establish and maintain an open ice pit. Journal of Cold Regions Engineering 28, 04014003. Colgan, W. & Arenson, L.U. 2013: Open-pit glacier ice excavation: brief review. Journal of Cold Regions Engineering 27, 223–243. Davis, R.M. 1967: Ice surface movement on the Tuto Ramp in North Greenland. U.S. Army Cold Regions Research & Engineering Labora- tory Technical Report 164, 24 pp. Els, F. 2012: You want ice with that? Centerra dives 18% aft er saying waste and ice will cut Kumtor production by 200,000 oz. Mining.com, 27 March 2012. http://www.mining.com/you-want-ice-with-that-center- ra-dives-18-aft er-saying-waste-and-ice-will-cut-kumtor-production-by- 200000-oz. Fausto, R.S., van As, D. & the PROMICE project team 2012: Ablation observations for 2008–2011 from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE). Geological Survey of Denmark and Greenland Bulletin 26, 73–76. Fettweis, X., Franco, B., Tedesco, M., van Angelen, J.H., Lenaerts, J.T.M., van den Broeke, M.R. & Gallée, H. 2013: Estimating the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MAR. Th e Cryosphere 7, 469–489. Joughin, I. Smith, B.E., Howat, I.M. Scambos, T. & Moon, T. 2010: Greenland fl ow variability from ice-sheet-wide velocity mapping. Jour- nal of Glaciology 56, 415–430. Lewis, S.M. & Smith, L.C. 2009: Hydrologic drainage of the Greenland ice sheet. Hydrological Processes 23, 2004–2011. Liang, Y.L., Colgan, W., Lv, Q. Steff en, K., Abdalati, W., Stroeve, J., Gal- laher, D. & Bayou, N. 2012: A decadal investigation of supraglacial lakes in West Greenland using a fully automatic detection and tracking algo- rithm. Remote Sensing of Environment 123, 127–138. Mayer, C. & Schuler, T.V. 2005: Breaching of an ice dam at Qorlortossuup tasia, south Greenland. Annals of Glaciology 42, 297–302. Nye, J.F. 1952: Th e mechanics of glacier fl ow. Journal of Glaciology 2, 82–93. Phillips, T., Rajaram, H., Colgan, W., Steff en, K. & Abdalati, W. 2013: Evaluation of cryo-hydrologic warming as an explanation for increased ice velocities in the wet snow zone, Sermeq Avannarleq, West Green- land. Journal of Geophysical Research, Earth Surface 118, 1241–1256. Rennermalm, A.K., Smith, L.C., Chu, V.W., Box, J.E., Forster, R.R., van den Broeke, M.R., van As, D. & Moustafa, S.E. 2013: Evidence of meltwater retention within the Greenland ice sheet. Th e Cryosphere 7, 1433–1445. Satke, R. & Galdini, F. 2014: EBRD’s environmental policy under scru- tiny in Kyrgyzstan. Th e Diplomat, 17 November 2014. http://thedip- lomat.com/2014/11/ebrds-environmental-policy-under-scrutiny-in- kyrgyzstan Smart, C.C., Owens, I.F., Lawson, W. & Morris, A.L. 2000: Exceptional ablation arising from rainfall-induced slushfl ows: Brewster Glacier, New Zealand. Hydrological Processes 14, 1045–1052. Smith, L.C. et al. 2015: Effi cient meltwater drainage through supraglacial streams and rivers on the southwest Greenland ice sheet. PNAS 112, 1001–1006. Th omsen, H.H., Th orning, L. & Olesen, O.B. 1989: Applied glacier re- search for planning hydro-electric power, Ilulissat/Jakobshavn, West Greenland. Annals of Glaciology 13, 257–261. Th omsen, H.H., Braithwaite, R.J., Weidick, A. & Olesen, O.B. 1993: Evaluation of hydropower potential for possible future industrial use, Nuuk area, West Greenland. Rapport Grønlands Geologiske Undersøgelse 159, 59–62. Van As, D. et al. 2014: Increasing meltwater discharge from the Nuuk region of the Greenland ice sheet and implications for mass balance (1960–2012). Journal of Glaciology 60, 314–322. Weidick, A. & Th omsen, H.H. 1986: A decade of glacier investiga- tions for utilisation of Greenland hydropower. Rapport Grønlands Geologiske Undersøgelse 128, 157–169. http://www.mining.com/you-want-ice-with-that-centerra-dives-18-after-saying-waste-and-ice-will-cut-kumtor-production-by-200000-oz./ http://thediplomat.com/2014/11/ebrds-environmental-policy-under-scrutiny-in-kyrgyzstan/ << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /PageByPage /Binding /Left /CalGrayProfile (Dot Gain 15%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (Coated FOGRA27 \050ISO 12647-2:2004\051) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Warning /CompatibilityLevel 1.7 /CompressObjects /Off /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages false /CreateJobTicket true /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.1000 /ColorConversionStrategy /LeaveColorUnchanged /DoThumbnails true /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 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