cold regions science and technology ELSEVIER Cold Regions Science and Technology22 (1994) 243-251
Hydrophilic liquid in glacier boreholes
V.S. Zagorodnov a,*, V.A. Morev b, O.V. Nagornov c, J.J. Kelley d, T.A. Gosink d, B.R. Koci d alnstitute of Geography, the Russian Academy of Sciences, 29 Staromonetny per., Moscow, 109017, Russia bArctic and Antarctic Research Institute, 38 Bering Str., St. Petersburg, 199226, Russia CMoscow Engineering Physics Institute, 31 Kashirskoe Shosse, Moscow, 115409, Russia dpolar Ice Coring Office, University ofAlaska Fairbanks, Fairbanks, AL 99775-1710, USA Received 22 December 1992; accepted after revision 9 August 1993)
Abstract
Environmental impact is a primary criterion for selecting any liquid used for filling boreholes in glaciers. Anti- freeze solutions based on ethanol and other high molecular weight alcohols are among several potential fluids used for drilling deep holes in the Arctic and Antarctic glaciers. At relatively high ice temperatures in boreholes, the concentration of ethanol in the solution can be low. Therefore, using such drilling fluids causes less environmental impact. Ethanol-water solutions (EWS) have been used for filling boreholes at various temperatures from 0 to - 58 ° C (Morev et al., 1988; Zagorodnov, 1988a; Zotikov, 1979 ). Ethanol requirements for deep drilling are sig- nificantly less than the volume of the borehole. Under normal operating conditions, ice core dissolution is about 1-mm ply per 40 min. Use of EWS for thermal drilling leads to slush formation. However, experience has shown that this is not a major drilling problem. The lifetime of the boreholes in central Antarctica is not less than one year.
1. Introduction mental impact (Gosink et al., 1991 a). In recent years, new liquids for filling boreholes have been When drilling in glaciers, the boreholes must tested in different countries. Hopefully, these will be filled with a non-freezing liquid to compen- be free of many of the drawbacks. sate for hydrostatic pressure. The liquids need to For the last twenty years, EWS has been used satisfy the following conditions: ( 1 ) low ecolog- for thermal drilling of deep holes in glaciers at ical impact and personal safety; (2) low ice core temperatures (Ti) from 0 to - 58 °C (Korotkev- contamination; (3) low viscosity; (4) should not ich et al., 1979; Morev et al., 1988; Raikovskiy damage instrument components. et al., 1990; Zagorodnov, 1988a,b; Zotikov, Currently, oil-based liquids are widely used for 1979 ). The deepest borehole (870 m) has been filling deep holes in glaciers (Gundestrup, 1988; drilled by antifreeze thermal electrical drill Kudriashov et al., 1984). Such liquids have the (ATED) in central Antarctica filled with an advantage of low viscosity, but they have a num- EWS. At 800.6 m depth the drilling has been ber of drawbacks, including a negative environ- stopped for eleven months and the operation was resumed without any difficulty (Morev et al., *V.S. Zagorodnov is presently a visiting research professor at 1988). On the Amery Ice Shelf, a 252-m deep PICO, University of Alaska Fairbanks. borehole, at a minimum temperature of
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-16.3°C, has also been preserved approxi- philic" liquids which have a tendency to com- mately eleven months, after which drilling was bine with ice and dissolve it at temperatures be- continued (Raikovskiy et al., 1990). The bore- low 0 ° C. The term "hydrophilic liquid" implies hole at Dome B location (central Antarctica, the major dissimilarity from other types of drill- Ti= -58°C, pore close-off 120 m) reached 780 ing fluids (DFA, kerosene, and butyl acetate) m depth in 1988 after seven weeks of drilling. which have antagonistic or hydrophobic tend- Four years later, only the upper 40 m of the hole encies (i.e., they do not combine with ice). have been accessible. The ethanol requirement If the quantity of ice is infinite and the quan- varied from 3 to 80% ofborehole volume. Mea- tity of ethanol is finite, a thermodynamic equi- surements indicate that the temperature of the librium will occur: T= Te, and C= Coq, where Te, EWS in the borehole comes to a stable equilib- and Ceq are the equilibrium temperature and rium 120 hr after drilling is finished (Zagorod- concentration, respectively. If one of these con- nov and Arkhipov, 1990). ditions breaks down, ice dissolution or ice for- Two major advantages of the EWS attract at- mation will occur. Equilibrium of the EWS in the tention: ( 1 ) environmental and personal safety boreholes can be reached when Toq = Ti. The ex- and (2) low ethanol requirements. However, perimental relationship approximated by when thermal drilling has been performed at gla- C~q=-0.01334T~q, (-60°C
eral properties of EWS, mechanisms of slush for- o mation and methods of its removal are consid- ~-4 -lO ered. The causes of ethanol penetration into the ice core are discussed. 20 © 3O 2. Physical properties of ethanol-water solutions 4O The freezing point of the water solutions of al- I i i~- CO -50 ------I q-- --T2~ cohols, acids, sodium chloride, dextrose, sucrose I I I \, and others is below 0°C (Eggers et al., 1964; -60 ___1 _ ~ _ ± .Xq Pauling, 1970). The freezing point of pure ethyl alcohol is -114°C. It is the so called "hydro- Fig. 1. Equilibrium temperature of EWS. KS. Zagorodnov et al. I CoM Regions Science and Technology 22 (1994) 243-251 245
1000 II hole and therefore the EWS equilibrium is dis- turbed. Antifreeze solutions at temperatures
? 980 L _ higher than Teq melt the surrounding ice (Gos- I ink et al., 1991a). As the solution cools, water
_~ 960 • L___ refreezes out of solution and Teq approaches Ti. Lamella- and needle-shaped ice crystals freeze out b from the solution, producing slush. The follow- ~ 940 ___ L _ E ing estimations are based on the borehole and (1) C2 k drill parameters presented in Table 1 and the 920 :I L_ _ temperature distribution shown in Fig. 4. The I I heat generated by the instrument is presented 900 ...... I ...... I ...... I -60 -40 -20 0 here as quantity of ice which can be melted from the borehole wall. Temperature (Teq), °C
Fig. 2. Density of the EWS at the equilibrium temperature. Table 1 Drill and borehole parameters used in estimations of ice slush I00 quantities formed during drilling of polar glaciers. I I EWS i i -~ 80 -- _ L _ _ L _ _ _ Hole depth Hbh = 3,700 m Hole diameter 2Ro = 120 mm O i~. I Core diameter= 80 mm 60 Power of the heating bit Ph = 2.6 kW Heater efficiency = 85% >~ *X I Energy losses in cable AP= 0.5Ph = 1.3 kW Rate of drilling-melting Sm= 5 m/h Drill mass Ma = 100 kg .~ 2o ___L _L:~- Mass of 1 m of cable Mc = 0.28 kg > Butyl ~JET A 11.-- Length of ice core, taken during one run L = 6 m
-60 50 -40 -30 -20 -10 0 Temperature (Teq), °C Temperature, °C 60 -40 -20 Fig. 3. Viscosity of EWS at equilibrium temperature com- o ,, ,~ ...... ~ pared with JET A-1 and butyl acetate. po /1% and butyl acetate (Gosink et al., 1991a) are _ kLk .... ,_L _ 1000 \ \ i i / I shown for comparison in Fig. 2. Nevertheless, in F~ \ F I , I the range of temperature from 0 to -25°C the E lowering speed of the thermal drill (length 3.2 2000 - - ! X R L\_ 7/L • _ --~ X[ \ t I m, weight 60 kg) has been 0.4 m/s (Zotikov, 1979 ), At a temperature of - 53 °C (Antarctica, @ / ~."x \I\ I Komsomolskaya Station) the lowering speed of 3000 ~ -F- - ~ ~ ~ - I / I I\~\ ~ I the drill (length 5.5 m, weight 100 kg) was about ~t ~ F I 0.2 m/s. Drilling performance on an 800-m deep I I I I 4000 ...... borehole in central Antarctica demonstrates a 70- 900 920 940 960 980 1000 m/week penetration rate (one 12-hr shift). Density, kg/m a i ...... i ...... i .... iJillt,l,,llJl,i ...... lxJ 0.0 0.2 0.4 0.6 0.8 1.0 3. Slush formation EWS concentration Thermal drilling operation is accompanied by Fig. 4. Calculated temperature of ice (Ti), density (Pc), and heat release along the whole length of the bore- concentration (Ceq) of EWS in the borehole. 246 KS. Zagorodnov et al. ~Cold Regions Science and Technology 22 (1994) 243-251
3.1. Heat losses during the drilling-melting the solution will be expended for ice melting, then process the concentration of EWS comes to T~q. Then the mass of ice dissolved on the borehole wall (mi) About 15% of the heat generated by the heat- will be as follows: ing bit is consumed on warming the ice around mi = O. 15APHbh/( Sm,~ ) ( 3.1 ) the borehole wall, core and drilling solution dur- ing drilling. Calculations based on the tempera- where Sm is the rate of drilling-melting 2 is the ture of the solution just after drilling and the latent heat of dissolution. Therefore, when drill- equilibrium temperature of the solution (Figs. 5 ing to a depth of 3,700 m, about 1.7 m 3 of ice and 6 ) indicate that about half of the heat energy could be dissolved. is consumed for heating the solution inside the borehole and the rest for heating the core and the 3.2. Energy losses in the electric cable hole wall. If we assume that the surplus energy in Approximately half of the transmitted energy is lost to electrical resistance in the cable, thus Tempera[ure, °C heating of the cable and the surrounding solu- -10 -8 -6 -4 -2 0 o tion causes dissolution of the ice from the bore- I hole wall. Experimental data (Figs. 5 and 6) I I show that about 60 hr after drilling, the temper- I ature of the solution reaches equilibrium, having 1°°I a I dropped by about 0.2 ° C. If all of the cable heat I 200 was consumed for heating of the solution and thus for melting ice from the borehole wall, then:
300 mi = APHbh/ ( 2SrnJ. ) (3.2) I ¢J I r-h In reality, when the cable is lowered from depth 400 I z to z+dz, the mass of ice dissolved is equal to I I dmi=APzdz/(Sm2). The mass of ice formed I I 500 I I during refreezing is obtained by integrating this I b°tt°m I ,~ equation from 0 to Hbh. During the entire drill- I 566,7 ml 600 ing time, the volume of ice could be dissolved from the wall could be as much as 23 m 3. Fig. 5. Temperature distribution in the Austfonna borehole: (a, b, c) measured after break of drilling on respective depth; (d) measured after input of additional ethanol to the 3.3. Heat transfer by instrument passage borehole. In the central part of the Antarctic Ice Sheet near the surface, Ti = - 50 to - 60 ° C; Ti at the bottom is close to the melting point of ice (Fig. l Austfonna , I glacier 4). Under these conditions, when moving along -6 - • - - the borehole the drill and cable will transfer heat. --~ I When the cold drill and cable are lowered into © 7 ~ • .... : the warmer layers, ice will form on their sur- faces. When raised, the warmer drill and cable will heat the EWS and the borehole wall will be 0 100 200 300 400 500 600 dissolved. If the borehole depth is 3,700 m, the Time, hours lowering and raising of the drill will take at least Fig. 6. Time-scale variation of the temperature in the Aust- two hours. Drilling a 6-m ice core will take about fonna borehole. one hour. Thus, in conditions of intensive hy- KS. Zagorodnov et aL / Cold Regions Science and Technology 22 (1994) 243-251 247 drodynamic heat exchange, there is ample time into the surrounding ice, a mathematical model for the drill and cable to reach ambient temper- of the interaction between the heated EWS and ature. Since T(z)=a+flz/Hbh (Fig. 4), where the ice wall was developed. Assuming that the or=-60, fl=57, and z=the current depth, the sum of all heat sources discussed above, radiates mass of ice formed or dissolved when the cable from an axial cable of diameter r0, the tempera- moves at a distance dz is dmi(z)=Cdcflzdz/ ture of the solution will rise and the thermody- (2H~h). Integrating from 0 to Zk, the mass of ice namic equilibrium will be disturbed. As a result, formed when the drilling depth is zk will be the ice wall will be dissolved, the ethanol concen- m (zk) = Cddl4cflz~ / ( 22Hb2h ). The total mass of tration will be lowered, and some portion of the ice could be dissolved by the cable displacement heat will penetrate the surrounding ice. If heat- during drilling is ing is stopped, then the initial position of the N phase boundary R0 will be re-established after mi = ~ m(Zk) some time t. If we simplify the problem by as- k=l suming cylindrical symmetry, then all variables N(N+ 1 ) (2N+ 1 )CdcM~flL 2 depend on the radius r and time t. The heat flow - 12)]J-/2h ( 3.3 ) in the borehole is then governed by OT { 02T 10T~ where Cdc is the specific heat of the material from --~-f~---Xm~-~F2"41-7~F) t>O, ro ki OT_k OT 2, 4. Correlation of the ice dissolution effect and Or '--~r = p'' thermal diffusivity in surrounding ice OC dR -D~r=C--~ r=R (4.6) To estimate the portion of heat energy going 248 KS. Zagorodnov et al. /Cold Regions Science and Technology 22 (1994) 243-251 along the radius does not exceed one to two K, _ks OT_ q and displacement of the phase boundary is much Or -2nro r=ro (4.7) less than the initial radius of the borehole. and Numerical solutions of the above problems at Qi = -k(OT/Or), and qi=0 are presented in Fig. C(R,t) = C~q (T) (4.8) 7 (ARm is the boundary displacement when where ks and ki are the thermal conductivities of qi=0). During one drilling run, a less than ethanol-water solution and of ice, respectively, ;t 1 × 10-3-mm thick ply of the borehole wall is is the latent heat of ice melting, and Pi is the den- dissolved. The calculations show that the heat sity of ice. conduction from the borehole into the surround- The above problem, defined by Eqs. (4.1) ing ice is about 98% of the total energy dis- through (4.8), was solved using finite-difference charged in the borehole. expansions of the derivatives and retaining ac- curacy in the first-order time derivative and sec- 5. Discussion ond-order spatial derivatives. If the heat flux from the heated mixture is consumed only for 5.1. Slush formation dissolution of ice (as in Sections 3.1 to 3.3 ), Eq. (4.6) is reduced to Actual thermal drilling operations (borehole depths of 570 to 720 m, ice temperatures of - 8 0T dR -k~--~r=2Pi dt r=R (4.9) to - 28 oC) have shown that the volume of slush is 3 to 5 times greater than the estimated volume Equations (4.1) through (4.5), (4.7) and (4.8) of dissolved ice obtained from Eqs. 4.1 to 4.8 are unaltered. (qi#0) and does not exceed 3% of the magni- For estimations, the following parameters were tude predicted by Eqs. 4.1 to 4.5 and 4.7 to 4.9 assumed: 2=3.3× 105 J/kg, Ti-265 K, pi=917 (qi = 0 ). It can be concluded that a large percent- kg/m 3, ki=l.33X10 -6 J/(m s K), ks= age of heat from the borehole goes into the sur- 1.5x10 -7 J/(m s K), Ro=0.06 m, ro= rounding ice. 4.3×10 -3 m, Zi=2.22 mE/s, Xm=0.53 mE/s, As the depth of drilling increases, the mass of D=l.5x 10 -8 J/(m s K), q=2 W/m. We also slush also increases, primarily due to the move- assumed that the parameters of the mixture are ment of equipment through the borehole. The constant because the absolute temperature drop number of drilling runs N increases linearly as depth increases, but the mass of ice formed is proportional to N 3. A decrease in core length L E 1 / I I f results in an increase of N=Hbh/L and ice mass / <1 I r/ / increases proportionally by 1/L. Decreasing both 10 ~ - L _ _ / --h _ _ the mass and heat capacity of the drill and cable Iqi=O~ , I ! / / J results in a proportional decrease in ice forma- lO .... L/_ _L /~/~l tion. Since only a small percentage of thermal l/ energy is consumed for ice dissolution, less than //I / qi~O q) i0 -3 _ J L _/ • _ 5.9 m 3 of ice slush will be formed (approxi- I ~ I / r mately of 5% of the calculated slush volume O) L J I/ 0 (qi # 0). Addition of ethanol into the borehole io % [J7' / -/ - - • - dissolves the slush. ah 10 -sL~ , , /, r ..... I ...... 5.2. Ice core contamination 0.80 1.20 1.60 2.00 Time, hours Penetration of ethanol up to 2.0 cm has been Fig. 7. Time dependencies of phase boundary displacement. measured in a core obtained by a mechanical drill KS. Zagorodnov et al. / Cold Regions Science and Technology 22 (I 994) 243-251 249 (Gosink et al., 1991 b ). Chemical analysis of ice ping the ice core will also diminish ice core cores obtained by thermodrilling in boreholes contamination. filled with kerosene at Vostok and Dome C sta- tions in Antarctica (Boutron et al., 1988), 5.3. High viscosity of E WS showedthat these admixtures also penetrated into the ice core up to 2.5 cm. The high viscosity of ethanol solutions slows We anticipate three reasons for ethanol pene- down deployment and retrieval of equipment in tration into the ice core: ( 1 ) micro-cracks at the the borehole. The speed of the drilling operation ice core subsurface layer; (2) putting the ice core can be increased by increasing the clearance be- into a plastic bag and thermal container imme- tween the drill and the hole wall (Augustin et al., diately after extraction from the core barrel (i.e., 1988 ). With a greater clearance (presumably by ethanol has not evaporated); ( 3 ) ice dissolution 180% of tested ATED), the speed of lowering and and prolonged diffusion of ethanol into the core raising the drill in the borehole will be 0.5 to 0.7 could occur during transportation when the tem- m/s. Under the above condition and at Ti below perature of the ice core increases. -25°C, a penetration rate of about 350 to 450 We suggest that ethanol has penetrated into the m/wk can be achieved when thermodrilling with ice cores taken by ATED. The sample prepara- a 6-m long core barrel is employed. tion technique enables the collection of a cleansed sample (rids the sample of admixtures) of the 5.4. Ethanol requirements ice core and obtains true values of isotope and microparticle composition (personal communi- If the temperature distribution in a glacier is cation with P.M. Grootes, L.G. Thompson, Y.K. known, the ethanol required for a borehole can Punning, R.A. Vaikmiae). Studies of micropar- be computed. If the borehole has a volume Vbh, ticle concentration and oxygen-isotope compo- the volume of ethanol required is sition of the J-9 ice core pointed out that below Hbh¢1 pore close-off the ice core is less subject to con- (5.1) tamination. Taking into account the &elevation V: Vbh/Hbh J Ceq(z)dz/lO0 gradient, the average values of fi~80 of the J-9 ice o core have good correlation with oxygen-isotope where Ceq(Z) is equilibrium concentration of composition of the Byrd Station ice core and ethanol at depth z. Taking into account the lin- Ross Ice Shelf shallow ice cores (Grootes and ear relationship between Ceq and T, and z and Ti, Stuiver, 1982, 1986, 1987; Thompson and Mos- one can obtain ley-Thompson, 1982; Clausen et al., 1979). The V= (0.5bfl+a+ba+ 273b) Vbh (5.2) Komsomolskaya Station (central Antarctica) ice core has been obtained by ATED. The ~80 pro- Substituting numerical values for the constants file of this ice core fits well with Vostok ice core a, b, a, fl, which were defined earlier, we get isotope profiles (unpublished data, V.I. Niko- V=0.44Vbh= 16.3 m 3. To dissolve Vi=2.94 m 3 laev, personal communication). Numerous of ice slush, an additional volume of ethanol (Va) studies of the oxygen-isotope composition of must be added to the borehole: Arctic ice cores obtained by ATED also demon- strated data reliability (Vaikmiae and Punning, Va - Ceq Pi Vi (5.3) 1984). 100-- Ceq pC The quality of the ice core can be significantly where C¢q is an equilibrium concentration of improved by reduction of thermal stress (Nagor- ethanol on the top of the borehole, Pi, PC are the nov et al., 1994). In this case, the ice core be- densities of ice and ethanol, respectively. If comes less fractured and ethanol penetration is Ceq=76°/0 (Figs. 1 and 4), the volume of addi- decreased. Evaporation of the EWS before wrap- tional ethanol required is Va = 0.19 Vi = 10.8 m 3. 250 V.S. Zagorodnov et al. ~Cold Regions Science and Technology. 22 (1994) 243-251 The total amount of ethanol required for drilling 7. List of symbols a 3700-m borehole is V= 0.73 Vbh = 27.1 m 3. Finally, the problems related to the specific properties of ethanol-water solutions at low a,b,c constants temperatures can be overcome by improving drill C=C(r,t) ethanol-water mixture design and maintaining an optimum ethanol- concentration water ratio in the borehole. More exact estimates Cdc the specific heat of the drill and of the ethanol consumption for drilling deep holes cable in low temperature glaciers will require further Ceq (T) equilibrium concentration theoretical and laboratory investigations on heat- D diffusivity coefficient and mass-exchange processes in boreholes filled g gravity acceleration with EWS. /-/be the borehole depth ks, ki thermal conductivity of ethanol- water solution and ice 6. Conclusions L the length of ice core m~ the mass of 1 m of cable EWS has a lower environmental impact com- Md the drill mass pared to many alternative drilling fluids, with me ethanol mass in unit volume of practically acceptable physical properties. The solution ethanol requirements for drilling deep boreholes mi, mw mass of surplus ice and water, in central Antarctica is approximately 75% of the respectively borehole volume. At glacier temperatures higher N number of drilling runs than -25 ° C, the ethanol requirement is less than e~ the power of the heating bit 50%. Ethanol contamination is not a great obsta- q thermal flux of cable cle for studies of oxygen isotope and micropar- thermal flux into surrounding ice ticle composition of ice cores taken by ATED at qi R current radius of the borehole temperatures ranging from - 2.1 to - 53 ° C. the initial borehole radius High viscosity of EWS and slush formation at Ro low temperatures is a major drawback of anti- ro radius of cable freeze thermal drilling methods. The major cause Sm the rate of drilling-melting of EWS equilibrium disturbance and slush for- Te. equilibrium temperature mation is the lowering and raising of equipment Ti temperature of the ice in the borehole. Approximately 98% of the heat V volume of ethanol generated in the borehole during drilling activity Vb~ volume of the borehole radiates into the surrounding ice. Vi formed volume of ice Greater clearance between the drill and the z the current depth borehole wall decreases hydraulic resistance and Zk drilling depth of run increases the lowering and raising rate of the drill. a, fl constants As a result, at temperature ranges of -25 to coefficient of volume expansion of -60°C, slush formation and percentage of the solution ethanol required will be decreased and the pen- AP energy losses in cable etration rate will be 250 to 450 m/wk. ARm displacement of phase boundary Presumably the addition of ethanol into the without heat conduction into sur- borehole yearly keeps the borehole open. rounding ice 2 the latent heat of dissolution P kinematic viscosity of the solution Pi, Pe density of ice and ethanol, respectively KS. Zagorodnov et al. / Cold Regions Science and Technology 22 (1994) 243-251 251 thermal diffusivity of ice Grootes, P.M. and Stuiver, M., 1987. Ice sheet elevation Xm thermal diffusivity of ethanol-water changes from isotope profiles. IAHS Publ., 170:267-281. mixture Gundestrup, N.S. 1988. Hole liquids. In: C. Rado and D. Beaudoing (Editors), Ice Core Drilling. Proceedings of The Third International Workshop on Ice Drilling Tech- nology, Grenoble, pp. 51-53. Acknowledgments Gundestrup, N.S., Johnsen, S.I. and Reeh, N., 1984. ISTUK, a deep ice core drill system. CRREL Special Report, SR 83-34, pp. 7-19. The authors are grateful to their colleagues Korotkevich, E.S., Savatiugin, L.M. and Morev, V.A., 1979. from PICO and the faculty members of the Uni- Trough drilling a shelf glacier in the region of Novola- versity of Alaska Fairbanks for cooperation in the zarev Station. Sovetskaia Antarcticheskaia Ekspeditsiia. development of new ice drilling technology that Informatsionni Builleten, 98, WDC No. 81001417. will protect the environment. Thanks to finan- CRREL No. 35001057. cial support from the National Science Founda- Kudriashov, B.B., Chistiakov, V.K., Pashkevich, V.M. and Petrov, V.N., 1984. Selection of a low temperature fillerd tion, the authors are participating in the im- for deep holes in the Antarctic Ice Sheet. CRREL Special provement of antifreeze-thermodrilling Report, SR 83-34, pp. 137-138. technology now continuing at the PICO facility Morev, V.A., Manevskiy, L.N., Yakovlev, V.M. and Zago- at the University of Alaska Fairbanks. The au- rodnov, V.S., 1988. Drilling with ethanol-based anti- thors also wish to thank the Institute of Marine freeze in Antarctic. In: C. Rado and D. Beaudoing (Edi- Science Publications staff for their assistance tors), Ice Core Drilling. Proceedings of The Third International Workshop on Ice Drilling Technology, with the technical editing and preparation of this Grenoble, pp. 110-113. paper. Nagornov, O.V., Zagorodnov, V.S. and Kelley, J.J., 1994. Ef- fect of a heated drilling bit and borehole liquid on ther- moelastic stresses in an ice core. In: Proc. 4th Int. Work- shop on Ice Drilling Technology, Tokyo, 1993, in press. Pauling, L. 1970. General Chemistry. Freeman, San Fran- References cisco, CA, 959 pp. Raikovskiy, Yu.V., Samoilov, O.Yu., Pron', N.P., Smirnov, Augustin, L., Donnou, D., Rado, C., Manouvrier, A., Girard, K.Ye. and Arkhipov, S.M., 1990. Glaciological investiga- C. and Ricou, G., 1988. Thermal ice core drill 4000. In: tions of the Amery Ice Shelf in 1987-1989. Academiia C. Rado and D. Beaudoing (Editors), Ice Core Drilling. Nauk SSSR. Institut Geografii. Materialy Glatsiologi- Proceedings of The Third International Workshop on Ice cheskikh Issledovanii, 68:5-8 (in Russian). Drilling Technology, Grenoble, pp. 59-65. Thompson, L.G. and Mosley-Thompson, E., 1982. Micro- Boutron, C.F., Patterson, C.C. and Barcov, N.I., 1988. As- particle concentration and size-distribution determina- sessing the quality of thermally drilled deep antarctic ice tion from the J-9 core, Ross Ice Shelf. Antarct. J. USA, cores for trace elements analysis. In: C. Rado and D. 17(5): 83-85. Beaudoing (Editors), Ice Core Drilling. Proceedings of Vaikmiae, R. and Punning, I.M., 1984. Isotope-geochemical The Third International Workshop on Ice Drilling Tech- investigations on glaciers in the Eurasian Arctic. In: W.C. nology, Grenoble, pp. 182-197. Mahaney (Editor), Correlation of Quaternary Chronol- Clausen, H.B., Dansgaard, W. and Nielsone, J.O. 1979. Sur- ogies, Symposium, York University, Toronto. Geo Books, face accumulation on Ross Ice Shelf. Antarct. J. USA, Norwich, pp. 385-393. 17(5): 68-72. Zagorodnov, V.S. 1988a. Recent Soviet activities on ice core Eggers, D.F., Jr., Gregory, N.W., Halsey, G.D., Jr. and Ra- drilling and core investigations in Arctic region. Bull. binovitch., B.S., 1964. Physical Chemistry. Wiley, Chich- ester, 783 pp. Glacier Res., 6: 81-84. Gosink, T.A., Tumeo, M.A., Koci, B.R. and Burton, T.W., Zagorodnov, V.S. 1988b. Antifreeze-thermodrilling of cores 199 la. Butyl acetate, an alternative drilling fluid for deep in Arctic sheet glaciers. In: C. Rado and D. Beaudoing ice-coring projects. J. Glaciol., 37 ( 125 ): 170-176. (Editors), Ice Core Drilling. Proceedings of The Third Gosink, T.A., Koci, B.R. and Kelley, J.J., 1991b. Aqueous International Workshop on Ice Drilling Technology, ethanol as an ice drilling fluid. PICO TR 91-2, University Grenoble, pp. 97-109. of Alaska Fairbanks, Fairbanks, AL, 12 pp. Zagorodnov, V. and Arkhipov, S., 1990. Studies of structure, Grootes, P.M. and Stuiver, M., 1982. Ross Ice Shelf and Dome composition and temperature regime of sheet glaciers of C oxygen-isotope analysis. Antarct. J. USA, 17 (5): 76- Svalbard and Severnaya Zemlya: methods and outcomes. 78. Bull. Glacier Res., 8: 19-28. Grootes, P.M. and Stuiver, M., 1986. Ross Ice Shelf oxygen Zotikov, I.A. 1979. Antifreeze-thermodrilling for core through isotopes and west Antarctic climate history. Quat. Res., the central part of the Ross Ice Shelf (J-9 Camp), Antarc- 26: 49-67. tic. CRREL Report 79-24.