the hans tausen drill design performance further developments and some lessons learned in the mid 1990s excellent results from the grip and gisp2 deep drilling projects in greenland opened up funding for continued ice coring efforts in antarctica epica and greenland northgrip the glaciology group of the niels bohr institute university of copenhagen was assigned the task of providing drilling capability for these projects as it had done for the grip project the group decided to further simplify existing deep drill designs for better reliability and ease of handling the drill design decided upon was successfully tested on hans tausen ice cap peary land greenland in 1995 the 5 0 m long hans tausen ht drill was a prototype for the 11 m long epica and northgrip versions of the drill which were mechanically identical to the ht drill except for a much longer core barrel and chips chamber these drills could deliver up to 4 m long ice cores after some design improvements had been introduced the berkner island antarctica drill is also an extended ht drill capable of drilling 2 m long cores the success of the mechanical design of the ht drill is manifested by over 12 km of good quality ice cores drilled by the ht drill and its derivatives since 1995

borehole imagery of meteoric and marine ice layers in the amery ice shelf east antarctica a real time video camera probe was deployed in a hot water drilled borehole through the amery ice shelf east antarctica where a total ice thickness of 480 m included at least 200 m of basal marine ice down looking and side looking digital video footage showed a striking transition from white bubbly meteoric ice above to dark marine ice below but the transition was neither microscopically sharp nor flat indicating the uneven nature at centimetre scale of the ice shelf base upstream where the marine ice first started to accrete marine ice features were imaged including platelet structures cell inclusions entrained particles and the interface with sea water at the base the cells are assumed to be entrained sea water and were present throughout the lower 100 150m of the marine ice column becoming larger and more prevalent as the lower surface was approached until near the base they became channels large enough that the camera field of view could not contain them platelets in the marine ice at depth appeared to be as large as 1 2 cm in diameter particles were visible in the borehole meltwater probably marine and mineral particles liberated by the drill but their distribution varied with depth

clean subglacial access prospects for future deep hot water drilling accessing and sampling subglacial environments deep beneath the antarctic ice sheet presents several challenges to existing drilling technologies with over half of the ice sheet believed to be resting on a wet bed drilling down to this environment must conform to international agreements on environmental stewardship and protection making clean hot water drilling the most viable option such a drill and its water recovery system must be capable of accessing significantly greater ice depths than previous hot water drills and remain fully operational after connecting with the basal hydrological system the subglacial lake ellsworth sle project developed a comprehensive plan for deep greater than 3000 m subglacial lake research involving the design and development of a clean deep ice hot water drill however during fieldwork in december 2012 drilling was halted after a succession of equipment issues culminated in a failure to link with a subsurface cavity and abandonment of the access holes the lessons learned from this experience are presented here combining knowledge gained from these lessons with experience from other hot water drilling programmes and recent field testing we describe the most viable technical options and operational procedures for future clean entry into sle and other deep subglacial access targets

new technique for access borehole drilling in shelf glaciers using lightweight drills this paper describes a new environmentally friendly drilling technique for making shortand long term access boreholes in shelf glaciers using lightweight drills the new drilling technique was successfully developed for installation of small diameter sensors under the ross ice shelf through 193m thick ice at windless bight mcmurdo ice shelf antarctica the two access boreholes were drilled and sensors installed in 110 working hours the total weight of the drilling equipment including the power system and fuel is 400 kg installation of small diameter sensors was possible for 1 8 6 hours after penetration through the glacier into the sea water beneath the new drilling technique does not require drilling fluid and therefore has minimal environmental impact it should permit access through ice shelf ice up to 350m thick or glaciers on grounded ice or subglacial lakes if there is no water permeable interface at the base modifications presented in this work of the drilling equipment and protocol will allow for 1 21 working hours for penetration through 200m of ice 2 installation of sensors up to 120mm in diameter and 3 drilling long term open boreholes through 400m thick ice in 100 working hours

epica dome c 2 drilling operations performances difficulties results the european project for ice coring in antarctica epica dome c 2 edc2 drilling was concluded on 21 december 2005 a few metres above bedrock the drilling was stopped both for environmental reasons and because of the drilling difficulties encountered in warm ice this paper describes in detail the progress and the performance of the epica drill including the procedures needed to penetrate into warm ice and their effects on core quality some drill technical data are also presented

site information and initial results from deep ice drilling on law dome antarctica the aim of deep ice drilling on law dome antarctica has been to exploit the special characteristics of law dome summit i e low temperature and high accumulation near an ice divide to obtain a high resolution ice core for climatic environmental studies of the holocene and the last glacial maximum lgm drilling was completed in february 1993 when basal ice containing small fragments of rock was reached at a depth of 1196 m accurate ice dating obtained by counting annual layers revealed by fine detail 18 o peroxide and electrical conductivity measurements is continuous down to 399 m corresponding to a date of ad 1304 sulphate concentration measurements made around depths where conductivity tracing indicates volcanic fallout allow confirmation of the dating for agung in 1963 and tambora in 1815 or estimates of the eruption date from the ice dating for the kuwae vanuatu eruption 1457 the lower part of the core is dated by extrapolating the layer counting using a simple model of the ice flow at the lgm ice fabric measurements show a large decrease 250 to 14 mm 2 in crystal size and a narrow maximum in c axis verticality the main zone of strong single pole fabrics however is located higher up in a broad zone around 900 m oxygen isotope 18 o measurements show holocene ice down to 1113 m the lgm at 1133 m and warm 18 o about the same as holocene ice near the base of the ice sheet the lgm holocene 18 o shift of 7 0 only 1 larger than for vostok indicates that law dome remained an independent ice cap and was not overridden by the inland ice sheet in the glacial

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

circulation and water masses beneath the northern ronne ice shelf antarctica 1 we present oceanographic data from beneath the northern ronne ice shelf the data were collected during the austral summer of 2002 2003 from four sites located near the ice front in the ronne depression they consist of conductivity temperature depth ctd profiles and time series from moored instruments that vary in length from 9 to 20 weeks a strong tidally modulated inflow of relatively fresh water was found at the eastern margin of the ronne depression this low density inflow powers high basal melt rates that are responsible for a substantially thinned area of ice shelf a northward flow of ice shelf water along the western margin of the depression the antarctic peninsula coast was inferred from the ctd data from the new ctd and current meter data and from published results from cruises along the ice front we suggest that the flows at the margins of the ronne depression establish east west density gradients that drive an anticyclonic circulation within the depression the barotropic component of the circulation forms a gyre of strength 5 105 m3 s 1 and occupies a bowl in the field of water column thickness in the northern portion of the depression all water masses sampled had temperatures below the surface freezing point and are therefore classified as ice shelf water the relatively complex nature of the oceanographic regime in the ronne depression is overlain by a seasonal variability that is hinted at by the available time series probably explaining the apparent absence of inflowing hssw at the time of the measurements

ice temperature and high geothermal flux at siple dome west antarctica from borehole measurements a verlical temperature profile through the west antarctic ice sheet wais at the summit of siple dome reveals an elevated geothermal flux this could be the root cause for the existence of a dynamic ice stream system in the wais siple dome is still frozen on its bed but adjacent ice streams have bed temperatures at the pressure melting point of ice although present day temperature increases due to climatic change do not have an immediate effect on the basal conditions that control the velocity of the ice indirect ellbcts like a rapid disintegration of the floating ice shelves or additional melt water input at the surface could give rise to speed up of the ice streams with an ensuing rise in sea level ongoing melt at the base of the ice and changes at the margins will allow continued rapid flow of the ice streams with a possibility of disintegration within a relatively short period of time of at least part of the wais

mexican site for k t impact crater research throughout the caribbean suggests that the geophysical anomalies in the yucatan first noted by penfield and camargo 1981 and called the chicxulub crater could be the site of the impact purported to have caused the k t extinctions a semicircular ring of sink holes known locally as cenotes which correlates with the geophysical anomalies has been identified and it is argued that the origin of the cenote ring is related to postimpact subsidence of the chicxulub crater rim if there is indeed a crater the region within the cenote ring corresponds to its floor and the crater rim diameter is probably larger than 200 km if confirmed as a site of impact the chicxulub crater would be the largest terrestrial impact crater known which is consistent with the uniqueness of the k t global catastrophe

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

nivlisen an antarctic ice shelf in dronning maud land geodetic glaciological results from a combined analysis of ice thickness ice surface height and ice flow observations extensive observations on nivlisen an ice shelf at antarctica s atlantic coast are analysed and combined to achieve a new quality description of its complex glaciological regime we generate models of ice thickness primarily from ground penetratingradar ellipsoidal ice surface height primarily from ers 1 satellite altimetry freeboard height by utilising precise sea surface information and ice flow velocity from ers 1 2 sar interferometry and gps measurements accuracy assessmentsare included exploiting the hydrostatic equilibrium relation we infer the apparent air layer thickness as a useful measure for a glacier s density deviation from a pure ice body this parameter exhibits a distinct spatial variation ranging from 2 m to 16 m which we attribute to the transition from an ablation areato an accumulation area we compute mass flux and mass balance parameters on a local and areally integrated scale the combined effect of bottom mass balance and temporal change averaged over an essential part of nivlisen is 654 170 kgm2a 1 which suggests bottom melting processes to dominate we discuss our results in view of temporal ice mass changes including remarks on historical observations basal processes near surface processes and ice flow dynamical features the questionfor temporal changes remains open from the data at hand and we recommendfurther observations and analyses for its solution

first access to the ocean beneath ekstromisen antarctica by means of hot water drilling a hot water drill developed during the past 2 years at alfred wegener institute was used to penetrate the ekstrom ice shelf several times near the georg von neumayer station the drilling operation was successful and the initial large diameter 35 cm allowed easy access to the ocean one hole was used to install an ultrasonic echo sounder which recorded the ablation at the ice shelf bottom continuously another hole was used for emplacement of a thermistor string throughout the 237 m thick ice shelf for ice temperature measurements several ctd profiles in the 175 m deepwater column and the analysis of water samples provided valuable data for the understanding of ice shelf ocean interactions

a new 122 mm electromechanical drill for deep ice sheet coring disc 1 design concepts the deep ice sheet coring disc drill developed by ice coring and drilling services icds under contract with the us national science foundation is an electromechanical drill designed to take 122 mm diameter ice cores to depths of 4000 m the conceptual design of the disc drill was developed in 2002 03 based on science requirements written by k taylor and the united states ice coring community and on engineering performance objectives detailed design of the drill began in june 2003 special attention was paid to building safety into the design and operation of the drill system the drill was designed and manufactured by a team of engineers and technicians from the university of wisconsin madison and various subcontractors with assistance from the science community the european ice drilling community and polar logistical support organizations icds successfully tested the drill in greenland in 2006 and will continue its development to meet the science objectives of the west antarctic ice sheet divide ice core project

the berkner island antarctica ice core drilling project we describe a project to retrieve a 948 m deep ice core from berkner island antarctica using relatively lightweight logistics and a small team the drilling operation over three austral summer seasons used electromechanical drilling technology described in detail from a covered shallow pit and a fluid filled borehole a basal temperature well below pressure melting point meant that no drilling problems were encountered when approaching the bed and the borehole penetrated through to the base of the ice sheet and sediment was retrieved from beneath the ice

drilling to the beds of the greenland and antarctic ice sheets a review we give a review of drilling to the beds of the greenland and antarctic ice sheets with a history of just a century we use a chronological rather than a geographical ordering to emphasize the way drilling has developed the review is divided into two parts core drilling and hole only drilling for access to the beds or the deep interior of the ice sheets this is an overview not a comprehensive report on each project while we have endeavoured to include all projects that fit our selection criteria we have not provided all the technical details

oceanographic conditions south of berkner island beneath filchner ronne ice shelf antarctica we have made oceanographic measurements at two sites beneath the southern filchner ronne ice shelf hot water drilled access holes were made during january 1999 allowing conductivity temperature depth ctd profiling and the deployment of instrument moorings the ctd profiles show that the entire water column is below the surface freezing point we estimate the summer flux of water between the two sites to be 2 106 m3 s 1 the summer potential temperature salinity properties of the water column suggest that this flow is part of a recirculation in the deepest part of the subice shelf cavity and the filchner depression the recirculation is driven by a combination of the melting of deep basal ice and the freezing that results from the depressurization of the cold buoyant water as it ascends the ice shelf base the source of the water was high salinity shelf water hssw produced in the ronne depression this is the water that provides the external heat necessary for the strong melting at the deep grounding lines in the vicinity of foundation ice stream instruments moored at the drill sites show that during the winter hssw formed on the berkner shelf flows beneath the ice shelf and largely displaces the recirculating water from the two sites this provides an externally driven through flow that is warmer nearer the surface freezing point and slower than the internal recirculation and which is low enough in density to escape the filchner depression

new oceanographic data from beneath ronne ice shelf antarctica oceanographic data have been obtained via an access hole made through ronne ice shelf the site which is the third in a series of similar studies lies 17 km west of korff ice rise where 825 m of ice overlies a 485 m deep water column measurements included conductivity and temperature profiles and an instrument mooring was deployed for long term measurements of currents temperature and conductivity at the sea floor there was a 150 m layer of well mixed water with a potential temperature and salinity of 1 97 c and 34 72 the water cooled and freshened towards the ice shelf base ultimately reaching 2 41 c and 34 51 the hydrographic and water current data imply a flow into the deepest part of the sub ice shelf cavity of about 200 000 m s 1 of the deeper relatively warm water which would be able to power an average basal melt rate of 0 2 m a 1 for the western portion of ronne ice shelf

carbonate porosity from s p traveltime ratios a twenty mile s wave seismic line was acquired on the northeastern shelf of the anadarko basin by the 1977 1978 conoco p wave s wave group shoot the resolution of the s wave section is at least as good as the resolution of a coincident p wave section acquired in 1975 the top and bottom of a collection of paleozoic carbonates called the hunton group can be identified on both sets of data p and s traveltimes and traveltime ratios delineate lateral variations in the thickness and average porosity of the hunton where the pore space is saturated with liquid a systematic increase in average porosity from less than 2 percent to about 11 percent correlates with an increase in the s p traveltime ratio from 1 84 to 1 96 the ratio decreases to values between 1 65 and 1 80 at two places along the line probably indicating that the pore space is partially gas saturated at these locations the data are consistent with the seismic response of a petrophysical model of the hunton in which a majority of the pore shapes are elongated rather than round

mechanisms of fast flow in jakobshavns isbrae west greenland part i measurements of temperature and water level in deep boreholes several holes were drilled to depths of 1500 1630 m along a profile across jakobshavns isbrae 50 km upstream from the calving front drilling was by hot water and required approximately 20 h the holes were rapidly closed by refreezing but it was possible to instrument them with thermistors and tilt sensors before this occurred near the margins of the ice stream the holes reached the bed and connected with the subglacial drainage system water level changes recorded in these holes are discussed in terms of the basal hydraulic system the temperature measurements show that the glacier is temperate based moreover extrapolation of a measured temperature profile and its curvature suggests that a temperate layer of substantial thickness may exist at the bed near the center of the ice stream there is a striking difference in the shapes of temperature profiles measured at different locations beneath the center line the temperature minimum is at a considerably smaller relative depth than near the margins but it is nearly the same in magnitude 22 1 c this may indicate a disproportionately large vertical stretching of the basal ice in the center of the ice stream since the basal ice is warmer and much less viscous than the ice above a thickening of that layer would cause a corresponding increase of surface velocity we presume that this mechanism contributes to the fast flow of jakobshavns isbrae

drilling comparison in warm ice and drill design comparison for the deep ice core drilling community the 2005 06 antarctic season was an exciting and fruitful one in three different antarctic locations dome fuji epica dml and vostok deep drillings approached bedrock the ice water interface in the case of vostok emulating what had previously been achieved at northgrip greenland summer 2003 and 2004 and at epica dome c2 antarctica season 2004 05 for the first time in ice core drilling history three different types of drill kems jare and epica simultaneously reached the depth of warm ice under high pressure after excellent progress at each site the drilling rate dropped and the drilling teams had to deal with refrozen ice on cutters and drill heads drills have different limits and perform differently in this comparative study we examine depth pressure temperature pump flow and cutting speed finally we compare a few parameters of ten different deep drills

the microstructure of polar ice part i highlights from ice core research polar ice sheets play a fundamental role in earth s climate system by interacting actively and passively with the environment active interactions include the creeping flow of ice and its effects on polar geomorphology global sea level ocean and atmospheric circulation and so on passive interactions are mainly established by the formation of climate records within the ice in form of air bubbles dust particles salt microinclusions and other derivatives of airborne impurities buried by recurrent snowfalls for a half century scientists have been drilling deep ice cores in antarctica and greenland for studying such records which can go back to around a million years experience shows however that the ice sheet flow generally disrupts the stratigraphy of the bottom part of deep ice cores destroying the integrity of the oldest records for all these reasons glaciologists have been studying the microstructure of polar ice cores for decades in order to understand the genesis and fate of ice core climate records as well as to learn more about the physical properties of polar ice aiming at better climate record interpretations and ever more precise models of ice sheet dynamics in this part i we review the main difficulties and advances in deep ice core drilling in antarctica and greenland together with the major contributions of deep ice coring to the research on natural ice microstructures in particular we discuss in detail the microstructural findings from camp century byrd dye 3 grip gisp2 northgrip vostok dome c edml and dome fuji besides commenting also on the earlier results of some pioneering ventures like the jungfraujoch expedition and the norwegian british swedish antarctic expedition among others in the companion part ii of this work faria et al 2014 the review proceeds with a survey of the state of the art understanding of natural ice microstructures and some exciting prospects in this field of research

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