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RADIX (Rapid Access Drilling and Ice eXtraction) is a prospecting drilling system that has been designed, realized and tested on polar ice sheets. The goal of RADIX is to provide rapid, deep access for sampling of ice and downhole physical measurements that inform about ice sheet age and history and the integrity of layering. A 20 mm access hole is drilled with a hydraulic coiled tubing system where the tube consists of a plastic hose. The ice cuttings are flushed to the surface in normal circulation, i.e., between the hose and borehole wall, and can be sampled for analysis. After drilling, a dedicated logger with a 15 mm diameter is deployed into the hole for measuring the geometric orientation of the hole, the temperature profile and the dust content in the surrounding ice (optical dust logger). The equipment has been tested and improved during six field projects in Greenland and Antarctica. It is designed to ultimately drill through a 3000 m ice sheet within roughly 1 week. The greatest depth reached so far was 324 m during the last field project at Little Dome C. [ABSTRACT FROM AUTHOR]

We here describe, document, and make available a wide range of data sets used for annual-layer identification in ice cores from DYE-3, GRIP, NGRIP, NEEM, and EGRIP. The data stem from detailed measurements performed both on the main deep cores and shallow cores over more than 40 years using many different setups developed by research groups in several countries and comprise both discrete measurements from cut ice samples and continuous-flow analysis data. The data series were used for counting annual layers 60 000 years back in time during the construction of the Greenland Ice-Core Chronology 2005 (GICC05) and/or the revised GICC21, which currently only reaches 3800 years back. Now that the underlying data are made available (listed in Table 1) we also release the individual annual-layer positions of the GICC05 timescale which are based on these data sets. We hope that the release of the data sets will stimulate further studies of the past climate taking advantage of these highly resolved data series covering a large part of the interior of the Greenland ice sheet. [ABSTRACT FROM AUTHOR]

We here describe, document, and make available a wide range of data sets used for annual layer identification in ice cores from DYE-3, GRIP, NGRIP, NEEM, and EGRIP. The data stem from detailed measurements performed both on the main deep cores and shallow cores over more than forty years using many different setups developed by research groups in several countries, and comprise both discrete measurements from cut ice samples and continuous-flow analysis data. The data series were used for the construction of the Greenland Ice-Core Chronology 2005 (GICC05) and/or the revised GICC21. Now that the underlying data are made available, we also release the individual annual layer positions of the GICC05 time scale which are based on these data sets. We hope that the release of the data sets will stimulate further studies of the past climate taking advantage of these highly resolved data series covering a large part of the interior of the Greenland ice sheet. [ABSTRACT FROM AUTHOR]

Abstract: Ice sheets and deep ice cores have yielded a wealth of paleoclimate information based on continuous dating methods while independent radiometric ages of ice have remained elusive. Here we demonstrate the application of (234U/238U) measurements to dating the EPICA Dome C ice core based on the accumulation of 234U in the ice matrix from recoil during 238U decay out of dust bound within the ice. Measured (234U/238U) activity ratios within the ice generally increase with depth while the surface areas of the dust grains are relatively constant. Using a newly designed device for measuring surface area for small samples, we were able to estimate reliably the recoil efficiency of nuclides from dust to ice. The resulting calculated radiometric ages range between 80ka and 870ka. Measured samples in the upper 3100m fall on the previously published age-depth profile. Samples in the 3200–3255m section show a marked change from 723–870ka to 85ka indicating homogenization of the deep ice prior to resetting of the (234U/238U) age in the basal layers. The mechanism for homogenization is likely enhanced lateral ice flow due to high basal melting and geothermal heat flux. [Copyright &y& Elsevier]

After the NEEM (Greenland) deep ice-core drilling was declared terminated with respect to developing stratigraphic climate reconstructions, efforts were turned toward collecting basal icesheet debris and, if possible, drilling into the bedrock itself. In 2010, several meters of banded debrisrich ice were obtained under normal ice-drilling operations with the NEEM version of the Hans Tausen (HT) drill, but further penetration was obstructed by a rock in the path of the drill head at 2537.36 m. During short campaigns in 2011 and 2012, attempts were made to penetrate further using various reinforced ice cutters mounted on the HT drill head, tailored to cut through rock. These had some success in penetrating coarse material, but produced severely damaged cutters. Additionally a 51 mm diameter diamond cutting tipped rock drill was adapted to fit the NEEM drill. With this device, several additional meters of core containing subglacial sediments, rocks and rock fragments were collected. With these tools 1.39 m of additional material were obtained during the 2011 field season, and 7.1 m during 2012. Subglacial water refreezing into the newly formed borehole hindered further penetration, and the bedrock interface was not reached before final closure of the NEEM Camp. [ABSTRACT FROM AUTHOR]