hot water drilling and bore hole closure in cold ice drilling bore holes in deep cold ice masses by hot water methods and maintaining these holes with sufficient diameter to allow down hole experimentation poses a major obstacle to the investigation of conditions beneath ice sheets and ice streams closure of the water filled holes by refreezing is the dominant difficulty in this paper we describe calculations of heat transfer from the drilling system to the ice and the subsequent time dependent motion of the phase boundary defining the bore hole wall results are presented with the view of optimizing the bore hole radius at depth for a fixed drill performance and a variable rate of drilling calculation of melting refreezing rates at the bore hole wall requires the use of a one dimensional time dependent numerical heat flow model with a distorting mesh which follows the changing hole size the delay of hole closure is discussed with a view to keeping holes open long enough to allow instruments to be lowered to the glacier bed while realizing that drilling system performance may be marginal because of logisitical and or expenditure constraints the relative merits of drilling a large hole which is very time consuming with a small drill and the use of water soluble antifreezes which have a history of creating plugs of ice slush are discussed a method of creating a stable hole filled with antifreeze in which ice slush does not occur is described the recent application of these theoretical ideas to the planning and implementation of successful hot water drilling programs in antarctica and greenland is also presented

a hot water ice coring drill a new method of ice core drilling uses an annulus of hot water jets to melt out a cylindrical ice core this lightweight device used in combination with a fast hot water drill can quickly obtain ice cores from any depth

age distribution and stratigraphy of glacier peak tephra in eastern washington and western montana united states tephra layers from williams lake fen wildcat lake and east wenatchee washington and kearns basin lost trail pass sheep mountain bog and marys frog pond montana were analyzed by electron mi

deep drilling at vostok station antarctica history and recent events deep drilling into the ice sheet at vostok station antarctica was started by specialists of the leningrad mining institute since 1991 st petersburg state mining institute in 1970 five deep holes were cored hole no 1 to 952 m hole no 2 to 450 4 m hole no 3g 3g 1 3g 2 to 2201 7 m hole no 4g 4g 1 4g 2 to 2546 4 m and hole no 5g 5g 1 to 3650 2 m depth drilling of hole 5g 1 is not yet complete the deep drilling at vostok station has had successes and problems all the deep holes at vostok have undergone at least one offset drilling operation because of problems with lost drills these deviations were made successfully using a thermal drilling technique several drilling records have been achieved at vostok station the deepest dry hole no 1 952 m was made during soviet antarctic expedition sae 17 in 1972 the deepest fluid filled hole no 5g 1 made by a thermal drill tbzs 132 reached 2755 m during sae 38 in 1993 the deepest fluid filled hole in ice no 5g 1 was drilled with a kems 132 electromechanical drill and was stopped above vostok subglacial lake at 3650 2 m depth during russian antarctic expedition rae 51 in 2006

disc drill and replicate coring system a new era in deep ice drilling engineering the deep ice sheet coring disc drill and replicate coring system rcs were designed and manufactured by ice coring and drilling services ice drilling design and operations group of the university of wisconsin madison the disc rcs is an electromechanical system designed to take 122 mm diameter ice cores from the main borehole and 108 mm diameter replicate ice cores to depths of 4000 m detailed design of the disc drill began in 2003 and the completed drill was tested in greenland in 2006 during five consecutive field seasons at west antarctic ice sheet wais divide 3405 m of ice core were drilled setting the us deep ice drilling record the rcs based on the disc drill was developed and built in 2010 11 tested in antarctica during the 2011 12 wais divide field season and tested further in madison wi during summer fall 2012 during the 2012 13 antarctic field season the system produced five azimuth and depth controlled deviations at four target depth levels a total of 285 m of replicate ice core was recovered in the first coring of its kind the entire main replicate ice core including ductile brittle and warm ice had excellent quality and satisfied the needs of the ice science community

transport direction of peoria loess in nebraska and implications for loess sources on the central great plains abstract in the midwestern united states large rivers draining the laurentide ice sheet lis were the most important sources of peoria loess deposited during the last glaciation loess deposition near those rivers may have responded primarily to ice sheet dynamics rather than direct effects of climatic change in contrast it has been proposed that thick peoria loess on the central great plains was derived mainly from unglaciated landscapes northwest of the main loess deposits in this study transport directions inferred from more than 600 measurements of peoria loess thickness in nebraska are used to test the hypothesis that much of the peoria loess on the great plains is nonglaciogenic a strong northwest to southeast thickness trend indicates that most peoria loess in nebraska was transported from one or more unglaciated northwestern source areas rather than from glacially influenced river floodplains the missouri river draining the lis the platte river draining alpine glaciers and the elkhorn river unglaciated basin were secondary sources their contribution is not detectable beyond a distance of 40 60 km peoria loess deposition on the central great plains was largely a direct response to climatic change in the unglaciated source region

the james ross island and the fletcher promontory ice core drilling projects following on from the successful project to recover an ice core to bedrock on berkner island similar drilling equipment and logistics were used on two further projects to recover ice cores to bedrock in the antarctic peninsula at james ross island a ship and helicopter supported project drilled to bedrock at 363m depth in a single season while a twin otter supported project drilled to bedrock at 654m depth again in a single season from fletcher promontory in both new projects drilling was from the surface with the infrastructure enclosed in a tent using an uncased partially fluid filled borehole

mount mazama eruption calendrical age verified and atmospheric impact assessed geochemical identification of mount mazama ash in the greenland ice sheet project 2 gisp2 ice core gives a calendrical age of 7627 150 cal yr b p 5677 150 b c for the eruption thus providing a more accurate early holocene stratigraphic time line than previously available the gisp2 record of volcanically derived sulfate suggests a total stratospheric aerosol loading between 88 and 224 mt spread over an 6 yr period following the eruption of mount mazama taking into account the likelihood of some tropospheric aerosol transport to greenland realistic estimates of the resulting atmospheric optical depth range from 0 6 to 1 5 these values may have produced a temperature depression of 0 6 to 0 7 c at mid to high northern latitudes for 1 3 yr after the eruption these results indicate that the 5677 b c eruption of mount mazama was one of the most climatically significant volcanic events of the holocene in the northern hemisphere we also calculate a maximum stratospheric cl release of 8 1 mt by the eruption which may have led to substantial stratospheric ozone depletion

the investigation and experience of using estisol 240 and coasol for ice core drilling continuous good quality deep ice cores provide excellent scientific data with which to reconstruct a past climate record for 800 ka at depths starting from 100m using an electromechanical drill a drilling liquid is essential for successful recovery of the very high quality ice cores demanded by modern scientific analysis techniques e g continuous flow analysis finding a suitable drill fluid for use at deep ice coring drill sites is not an easy task temperatures vary greatly not just from site to site but also at a site where the average mean temperature from surface to bedrock can vary from 55 c to 2 75 c in the past 60 years many fluids have been used with varying degrees of success but for various reasons are either unavailable are now considered unsafe and dangerous or are too environmentally damaging to be permitted here we report on our pre season investigation into possible candidate drill fluids with specific information concerning estisol 240 and coasol the rationale behind the redesign of our drill successfully used at northgrip greenland and epica dml antarctica the knock on effect of those changes and our field experience in greenland at flade isblink in 2006 and at neem in 2009 10

closure of deep boreholes in ice sheets a discussion the most frequently used relation between ice deformation rate and stress is the power law commonly called glen s flow law an in which a is an ice stiffness parameter and n is an empirical constant a can be estimated from the simple exponential relation a ea0e q rt where a 0 is a constant independent of temperature e commonly called the enhancement factor depends on ice crystal orientation impurity content and other factors q is the activation energy for creep r is the universal gas constant and t is the absolute temperature laboratory experiments yield values of a0 9 514 mpa 3 a 1 for secondary creep typical borehole closure experiments then give e 0 16 this low value probably results from the fact that when deforming into a borehole ice is subject to stresses that are inconsistent with the preferred orientation of c axes that has developed over many years under a stress configuration with no borehole present closure data from vostok hole 3g yield e 0 7 this higher value may reflect a unique stress environment yielding fabrics that are somewhat better oriented for borehole closure

dimethyl siloxane oils as an alternative borehole fluid finding a new safe and ecologically friendly borehole fluid is one of the most pressing problems for forthcoming ice drilling projects not all recent borehole fluids qualify as intelligent choices from safety environmental and other technological standpoints we propose the use of silicone oils as the borehole fluid the most suitable type of silicone oils for deep ice drilling are low molecular or volatile dimethyl siloxane oils dsos low molecular dsos are clear water white tasteless odorless neutral liquids they are hydrophobic and inert substances that are stable to water air oxygen metals wood paper plastics etc of the dsos class 2 grades of kf96 1 5cs and kf96 2 0cs most fully fit our criteria for choice as borehole fluids the final conclusion as to the suitability of dsos for ice deep drilling will be made after the experiments in a test borehole

the evolution of thermal structure and water chemistry in lake nyos abstract we collected a time series of physical and chemical data to gain a better understanding of the dynamics of lake nyos measurements of water and gas chemistry and temperature made during january march and may 1987 are compared to data taken in september 1986 just after the initial co 2 gas release there is no pattern of change in overall heat content of the lake although heat input to bottom waters 185 208 m has occurred at a rate of 1600 mw m 2 this increase in heat content translates to a change from 23 38 to 24 12 c at 200 m and can be explained by geothermal heat flow and addition of thermal spring water concentrations of ca 2 mg 2 na k fe 2 and alkalinity have increased only in bottom waters in situ lake processes such as sulfate and iron reduction are unable to account for the changes in alkalinity observed chemical changes are consistent with a scenario where slightly thermal soda water is being input to the bottom of the lake measurements of p co 2 at depth ranged from 18 to 28 of saturation and exhibited horizontal variability overall recharge of co 2 in bottom waters is negligible mainly because of increasing ion concentrations in bottom water total stability of the water column increased 33 from 48 800 j m 2 in september 1986 to 64 700 j m 2 in may 1987 as long as co 2 concentrations remain the same this level of stability is higher than could be disrupted by common limnologic or meteorologic processes there is thermal and chemical evidence that a buildup of dissolved iron and co 2 in bottom waters must have preceded the august 1986 gas release in addition a survey of all crater lakes in cameroon indicates that only lakes nyos and monoun contain high concentrations of dissolved iron and co 2 thus there is a low probability of any other cameroonian lake releasing a substantial volume of co 2

luminescence dating of loess from the northwest united states thermoluminescence tl and infra red stimulated luminescence irsl ages have been determined for loess from the columbia plateau region of southeast washington and northeast oregon u s a the irsl ed values and ages appear to be tending towards a maximum level lower than that of the tl ed values and ages in general the tl ages are in stratigraphic order and agree well with the age control in the form of 14c and tl dated tephra units derived from various eruptions of mount st helens

topographic and climatic influences on accelerated loess accumulation since the last glacial maximum in the palouse pacific northwest usa abstract topographic and climatic influences have controlled thick loess accumulation at the southern margin of the palouse loess in northern oregon juniper and cold springs canyons located on the upwind flank of the horse heaven hills are oriented perpendicular to prevailing southwesterly winds these canyons are topographic traps that separate eolian sand on the upwind side from thick accumulations nearly 8 m of latest pleistocene to holocene l1 loess on the downwind side silt and sand rich glacial outburst flood sediment in the umatilla basin is the source of eolian sand and loess for the region sediment from this basin also contributes to loess accumulations across much of the columbia plateau to the northeast downwind of cold springs canyon mt st helens set s and glacier peak tephras bracket 4 m of loess demonstrating that approximately 2500 g m 2 yr 1 of loess accumulated between about 15 400 13 100 cal yr b p mass accumulation rates decreased to approximately 250 g m 2 yr 1 from 13 100 cal yr b p to the present tephrochronology suggests that the bulk of near source palouse loess accumulated in one punctuated interval in the latest pleistocene characterized by a dry and windy climate

radix a minimal resources rapid access drilling system determining the expected age at a potential ice core drilling site on a polar ice sheet generally depends on a combination of information from remote sensing methods estimates of current accumulation and modelling this poses irreducible uncertainties in retrieving an undisturbed ice core of the desired age although recently perfected radar techniques will improve the picture of the ice sheet below future drilling sites rapid prospective drillings could further increase the success of deep drilling projects here we design and explore a drilling system for a minimum size rapid access hole the advantages of a small hole are the low demand for drilling fluid low overall weight of the equipment fast installing and de installing and low costs we show that in theory drilling of a 20mm hole to a depth of 3000m is possible in 4 days first concepts have been realized and verified in the field both the drill cuttings and the hole itself can be used to characterize the properties of the ice sheet and its potential to provide a trustworthy palaeo record a candidate drilling site could be explored in 2 weeks which would enable the characterization of several sites in one summer season

subglacial drilling at black rapids glacier alaska u s a drilling method and sample descriptions we employed a commercial wireline drill rig to investigate the subglacial conditions of black rapids glacier a well studied surge type glacier in the central alaska range the four main goals were to assess the capabilities of the commercial drilling industry for sampling subglacial material to investigate the basal morphology to determine the subglacial geology and to emplace borehole instruments the drilling was done in an area where seasonal and secular variations in speed are large and where seismic studies suggested the presence of a till layer four holes were drilled at three locations to a maximum depth of 620 m three holes yielded samples of basal ice and till although recovery of the latter was generally poor bedrock was sampled in one or possibly two of the holes in the area sampled the glacier is underlain by a till layer some 4 7 m thick confirming the seismic interpretation it consists ofa sandy matrix at least 20 30 of which comprises larger clasts limited samples ofthe matrix indicate that near the top ofthe till the porosity is 40 and that some of the pore water is frozen geologic studies suggest that the drilling area lies to the north of the denali fault a major tectonic boundary followed by the glacier and that most of the till is locally derived with transport distances of 2 km

promising new borehole liquids for ice core drilling on the east antarctic high plateau a drill liquid is essential for the purpose of recovering good quality scientifically useful ice cores at intermediate to deep depths i e 100m the pressure produced by the liquid helps to eliminate the detrimental effects of the abrupt release of isostatic pressure in the ice during the drilling process prevents consequential fractures within the ice core and is essential to produce an even distribution of hydrostatic pressure to balance the ice isostatic pressure and so minimize borehole deformation to perform these tasks while minimizing risks to health and the environment the liquid needs to exhibit specific physical chemical and biological characteristics here we report on two promising candidate drill liquids estisol 140 and estisol 165 for use in the extreme conditions found within the ice sheets of greenland and antarctica where the temperature can range from close to 0 c to below 57 c and pressures can exceed 40mpa from both the manufacturer s data and our laboratory tests and observations we report on the physical chemical and biological characteristics that both liquids exhibit we also report on how one of the candidates was field tested on the greenland ice sheet and the east antarctic high plateau

long history of pre wisconsin ice age cataclysmic floods evidence from southeastern washington state abstract cataclysmic ice age floods in the pacific northwest began as early as 1 5 2 5 ma on the basis of an evaluation of surface exposures and recent borehole studies within southeastern washington field evidence suggests at least two episodes of pre wisconsin i e 130 ka glacial outburst flooding a middle pleistocene flood is identified by normal magnetic polarity calcrete capped deposits that yield maximum th u age dates from 200 to 400 ka the deposits with reversed polarity are correlated to early pleistocene 780 ka floods while exposures of pre wisconsin deposits are limited because of erosion and or burial the record of earlier pleistocene flooding is preserved within giant flood bars these bars show incremental growth representing a composite from cataclysmic floods deposited intermittently through the pleistocene in one giant flood bar up to 100 m thick deposits interpreted as matuyama age indicate that the bar had grown to half its present height by 780 ka furthermore matuy

unprecedented last glacial mass accumulation rates determined by luminescence dating of loess from western nebraska abstract a high resolution chronology for peoria last glacial period loess from three sites in nebraska midcontinental north america is determined by applying optically stimulated luminescence osl dating to 35 50 m quartz at bignell hill nebraska an osl age of 25 000 yr near the contact of peoria loess with the underlying gilman canyon formation shows that dust accumulation occurred early during the last glacial maximum lgm whereas at devil s den and eustis nebraska basal osl ages are significantly younger 18 000 and 21 000 yr respectively at all three localities dust accumulation ended at some time after 14 000 yr ago mass accumulation rates mars for western nebraska calculated using the osl ages are extremely high from 18 000 to 14 000 yr much higher than those calculated for any other pre holocene location worldwide these unprecedented mars coincide with the timing of a mismatch between paleoenvironmental evidence from central north america and the paleoclimate simulations from atmospheric global circulation models agcms we infer that the high atmospheric dust loading implied by these mars may have played an important role through radiative forcing in maintaining a colder than present climate over central north america for several thousand years after summer insolation exceeded present day values

perspectives for development of ice core drilling technology a discussion abstract more than 170 years ago louis agassiz one of the creators of glacial theory made his firstattempt to drill into the bed of unteraargletscher swiss alps since that time various systems forthermal and mechanical drilling have been designed especially for boring into ice and someconventional drill rigs been adopted for ice coring although contemporary ice drilling knowledge andtechniques are now familiar there remain many problems to be solved by advanced moderntechnology specific challenges related to improving old drilling methods and developing new emergingtechnologies include 1 identification of depth limitation of dry drilling 2 improvement of casing 3 searching for the new environmentally friendly low temperature drilling fluids 4 reliableelimination of sticking drills 5 improvement of core quality in the brittle zone 6 additional coresampling from borehole walls after the core has been drilled 7 obtaining oriented core 8 designingautomation drilling systems 9 developing rapid access drills possible ways of solving these problemsare presented below keywords

borehole evidence for a thick layer of basal ice in the central ronne ice shelf the ronne ice shelf floating between berkner island and the antarctic peninsula is the biggest ice shelf in antarctica it drains an estimated 1 2 106km2 of the antarctic ice sheet much of it resting on bedrock below sea level consequently the balance and dynamics of this ice shelf is of importance to antarctic glaciology especially with regard to the integration of this part of the cryo sphere into the global processes that control the climate of the earth extensive radio echo sounding res by robin and others revealed reflections in the central part of the ronne ice shelf at the relatively shallow depth of 100 200 m below surface1 the interpretation of these echoes which varied in strength was ambiguous and the possibility of internal reflecting horizons was thoroughly discussed but after surface elevation measurements by radar altimeter from drifting balloons appeared to fit the presence of thin ice it was decided to base a thickness map of the ronne ice shelf on these res echoes1 4 we now present direct observational evidence from boreholes that the total ice thickness is much greater than mapped and that the shallow res reflections therefore do come from internal horizons

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

environmental considerations of low temperature drilling fluids the introduction of low temperature fluid into boreholes drilled in ice sheets helps to remove drilling cuttings and to prevent borehole closure through visco plastic deformation only special fluids or mixtures of fluids can satisfy the very strict criteria for deep drilling in cold ice the effects of drilling fluid on the natural environment are analyzed from the following points of view 1 occupational safety and health 2 ozone depletion and global warming 3 chemical pollution and 4 biological pollution traditional low temperature drilling fluids kerosene based fluids with density additives ethanol and n butyl acetate cannot be qualified as intelligent choices from the safety environmental and technological standpoints this paper introduces a new type of low temperature drilling fluid composed of synthetic estisol tm esters which are non hazardous substances estisol tm 140 mixtures with estisol tm 165 or estisol tm f2887 have an acceptable density and viscosity at low temperature to avoid the potential for biological contamination of the subglacial environment the borehole drilling fluid should be treated carefully on the surface