Recent studies have shown that stratigraphically disturbed meteoric ice bedded at Vostok Station between 3318 and 3539 m dates back to 1.2 Ma BP and possibly beyond. As part of the VOICE (Vostok Oldest Ice Challenge) initiative, a new deviation from parent hole 5G-1 was made at depths of 3270–3291 m in the 2018/19 austral season with the aim of obtaining a replicate core of the old ice. Sidetracking was initiated using the standard KEMS-132 electromechanical drill routinely employed for deep ice coring at Vostok, without significant changes to its initial design. Here we describe the method and operating procedures for replicate coring at a targeted depth in an existing slant hole, involving the use of a cable-suspended electromechanical drill. The design of the milling cutter head used for sidetracking is presented. The performance characteristics and the experience of drilling branch-hole 5G-5 at Vostok are described and discussed.

Significant upgrades to the Rapid Air Movement (RAM) Drill were developed and tested by the US Ice Drilling Program in 2016 through 2020 for the U.S. National Science Foundation. The design of the system leverages the existing infrastructure of the RAM Drill with the goal of greatly reducing the logistical burden of deploying the drill while maintaining the ability to drill an access hole in firn and ice to 100 m in 40 min or less. In this paper, characteristics of the drill are described, along with a description of the drill performance during the testing at Raven Camp in Greenland and at WAIS Divide Camp in Antarctica.

To understand the long-term climate and glaciological evolution of the ice sheet in the region bordering the Weddell Sea, the British Antarctic Survey has undertaken a series of successful ice core projects drilling to bedrock on Berkner Island, James Ross Island and the Fletcher Promontory. A new project, WACSWAIN, seeks to increase this knowledge by further drilling to bedrock on two further ice rises in this region. In a single-season project, an ice core was recovered to bedrock at 651 m on Skytrain Ice Rise using an ice core drill in a fluid-filled borehole. In a second season, a rapid access drill was used to recover ice chips to 323 m on Sherman Island in a dry borehole, though failing to reach the bedrock which was at an estimated depth of 428 m.

The Winkie Drill is an agile, commercially available rock coring system. The U.S. Ice Drilling Program has modified a Winkie Drill for subglacial rock and ice/rock interface coring, as well as drilling and coring access holes through ice. The original gasoline engine was replaced with an electric motor though the two-speed gear reducer and Unipress hand feed system were maintained. Using standard aluminum AW34 drill rod (for 33.5 mm diameter core), the system has a depth capability of 120 m. The drill uses forward fluid circulation in a closed loop system. The drilling fluid is Isopar K, selected for favorable properties in polar environment. When firn or snow is present at the drill site, casing with an inflatable packer can be deployed to contain the drill fluid. The Winkie Drill will operate from sea level to high altitudes and operation results in minimal environmental impact. The drill can be easily and quickly assembled and disassembled in the field by two people. All components can be transported by Twin Otter or helicopter to the field site.

An intermediate-depth (1751 m) ice core was drilled at the South Pole between 2014 and 2016 using the newly designed US Intermediate Depth Drill. The South Pole ice core is the highest-resolution interior East Antarctic ice core record that extends into the glacial period. The methods used at the South Pole to handle and log the drilled ice, the procedures used to safely retrograde the ice back to the National Science Foundation Ice Core Facility (NSF-ICF), and the methods used to process and sample the ice at the NSF-ICF are described. The South Pole ice core exhibited minimal brittle ice, which was likely due to site characteristics and, to a lesser extent, to drill technology and core handling procedures.

Rapid Access Ice Drill is a new drilling technology capable of quickly accessing the glacial bed of Antarctic ice sheets, retrieving ice core and rock core samples, and providing boreholes for downhole logging of physical properties. Scientific goals include searching for old ice near the glacial bed and sampling subglacial bedrock. During field trials near McMurdo Station on a piedmont glacier at Minna Bluff in the 2019–20 austral summer, we successfully completed a ‘top-to-bottom’ operational sequence in three boreholes by (1) augering through firn, (2) creating a borehole packer seal in non-porous ice, (3) establishing fluid circulation, (4) quickly drilling a borehole in ice at penetration rates up to 1.2 m min−1, (5) acquiring a short ice core at depth, (6) penetrating the glacial bed at a depth of ~677 m, (7) recovering a 3.2 m core of ice, basal till and subglacial bedrock, (8) optically logging the borehole on wireline, (9) testing hydrofracture potential by overpressuring the borehole fluid and (10) operating in an environmentally benign yet rapid field mode. Minna Bluff testing, therefore, demonstrates the effectiveness of this integrated system to drill rapidly through thick ice and penetrate across the glacial bed to take cores of bedrock.

The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

Using significant technological breakthroughs and unconventional approaches, the goal of the in situ probing of glacier ice for a better understanding of the orbital response of climate (SUBGLACIOR) project is to advance ice core research by inventing, constructing and testing an in situ probe to evaluate if a target site is suitable for recovering ice as old as 1.5 million years. Embedding a laser spectrometer, the probe is intended to make its own way down into the ice and to measure, in real time and down to the bedrock, the depth profiles of the ice δD water isotopes as well as the trapped CH4 gas concentration and dust concentration. The probe descent is achieved through electromechanical drilling combined with continuous meltwater sample production using a central melting finger in the drill head. A key aspect of the project lies in the design and implementation of an efficient method to continuously transfer to the surface the ice chips being produced by the drill head and from the refreezed water expulsed downstream from the melting finger, into the borehole. This paper presents a detailed calculation and analysis of the flow rates and pressure conditions required to overcome friction losses of the drilling fluid and to effectively transport ice chips to the surface.

We drilled an 81.2-m-long ice core in the accumulation area (5860 m a.s.l.) of Trambau Glacier in the Rolwaling region during October–November 2019. The drilling operation was conducted with a lightweight electro-mechanical drill system after two reconnaissance fieldworks in 2017 and 2018, during which two shallow firn cores were drilled with a hand auger. The drill system and ice core samples were transported by helicopters at a high elevation of 6000 m a.s.l. A further challenging issue was the ice core transportation between Nepal and Japan, as no regular commercial flight was available for the frozen samples. The addition of dry ice imported from India immediately prior to leaving Nepal allowed the ice core samples to be successfully transported to a cold room in Japan, and remain in a frozen state. Stratigraphic observations during the drilling operation suggest the drill site has been affected by melting and refreezing.

Recently, innovations in ice drilling have yielded considerable improvements to existing drilling techniques, as well as innovative drilling technologies that can be used in new types of applications. However, some specific challenges have to be addressed for improving existing drilling methods and developing new ones: (1) combination and unification of different drilling systems; (2) facilitating ice core breaking; (3) improving existing systems and developing new rapid-access ice drilling systems; (4) reliable elimination of ice hydraulic fracturing problems; (5) developing new environment-friendly methods of drilling in the sub-glacial lake sediments; and (6) design of unconventional ice drilling systems. Possible solutions to these problems are presented herein.

In glaciology, snow–firn temperature at 10 m is considered a representation of the mean annual air temperature at the surface (MAAT) of the studied site. Although MAAT is an important parameter in ice-sheet investigations, it has not been widely measured in Antarctica. To measure the 10 m snow–firn temperature in Antarctica, a shallow hot-point drill system is designed. In this simple and lightweight system, a hot-point drill can melt boreholes with a diameter of 34 mm in the snow–firn to a depth of 30 m and a temperature sensors string can measure the borehole temperature precisely. In the 2018/19 field season, 16 boreholes along the Zhongshan–Dome A traverse were drilled, and the borehole temperature was measured. Although certain problems existed pertaining to the hot-point drill, a total depth of ~244 m was successfully drilled at an average penetration rate of ~10 m h−1. After borehole drilling, ~12–15 h were generally required for the borehole to achieve thermal equilibrium with the surroundings. Preliminary results demonstrated that the 10 m snow–firn temperature along the traverse route was affected by the increasing altitude and latitude, and it decreased gradually with an increase in the distance from Zhongshan station.

Hot-point drills have been widely used for drilling boreholes in glaciers, ice caps and ice sheets. A hot-point drill melts ice through the thermal head at its bottom end. Penetration occurs through a close-contact melting (CCM) process, in which the ice is melted, and the meltwater is squeezed out by the exerted force applied on the thermal head. During the drilling, a thin water film is formed to separate the thermal head from the surrounding ice. For the hot-point drill, the rate of penetration (ROP) is influenced by several variables, such as thermal head shape, buoyancy corrected force (BCF), thermal head power (or temperature) and ice temperature. In this study, we developed a model to describe the CCM process, where a constant power or temperature on the working surface of a thermal head is assumed. The model was developed using COMSOL Multiphysics 5.3a software to evaluate the effects of different variables on the CCM process. It was discovered that the effect of thermal head shape and the cone angle of conical thermal head on ROP is less significant, whereas the increase in the BCF and the power (or temperature) of the thermal head can continuously enhance the ROP.

Water-filled boreholes in cold ice refreeze in hours to days, and prior attempts to keep them open with antifreeze resulted in a plug of slush effectively freezing the hole even faster. Thus, antifreeze as a method to stabilize hot-water boreholes has largely been abandoned. In the hot-point drilling case, no external water is added to the hole during drilling, so earlier antifreeze injection is possible while the drill continues melting downward. Here, we use a cylindrical Stefan model to explore slush formation within the parameter space representative of hot-point drilling. We find that earlier injection timing creates an opportunity to avoid slush entirely by injecting sufficient antifreeze to dissolve the hole past the drilled radius. As in the case of hot-water drilling, the alternative is to force mixing in the hole after antifreeze injection to ensure that ice refreezes onto the borehole wall instead of within the solution as slush.

This article presents the main aspects of the design solutions (based on the application of sensors MEMS and cantilevers), testing and applying of the multi-functional borehole logger ANTTIC (Antarctic Thermo-barometer, Inclinometer, Caliper) for geophysical high-precision monitoring (when simultaneous registering of temperature, pressure, axis inclination angle and radii of borehole cross-sections at 12 points), which is designed specifically for ultra-low temperatures and ultra-high pressures, and to determine an elliptical borehole shape and registration anisotropy factor in deep ice boreholes in the central region of Eastern Antarctica, in the areas of dome A at the Kunlun station (China) and/or of lake Vostok at the Vostok station (Russia).

Subglacial sediments have the potential to reveal information about the controls on glacier flow, changes in ice-sheet history and characterise life in those environments. Retrieving sediments from beneath the ice, through hot water drilled access holes at remote field locations, present many challenges. Motivated by the need to minimise weight, corer diameter and simplify assembly and operation, British Antarctic Survey, in collaboration with UWITEC, developed a simple mechanical percussion corer. At depths over 1000 m however, manual operation of the percussion hammer is compromised by the lack of clear operator feedback at the surface. To address this, we present a new auto-release-recovery percussion hammer mechanism that makes coring operations depth independent and improves hammer efficiency. Using a single rope tether for both the corer and hammer operation, this modified percussion corer is relatively simple to operate, easy to maintain, and has successfully operated at a depth of >2130 m.

In this paper, we present an electric-thermal drill with a novel design of a melting head that was developed within the EnEx-RANGE project. The design combines a short melting head with a large surface area of parabolic shape. It was succesfully tested in the laboratory as well as on Alpine glaciers (Langenferner and Mittelbergferner) and at the Ross Ice Shelf in Antarctica. In all these different environments, a high melting speed per specific power of typically 8.8 cm3 w−1 h−1 is achieved that is close to the ideal maximum bound of ~10.5–11.8 cm3 w−1 h−1 when neglecting all heat losses. It has also been demonstrated that the melting probe can be operated with typical equipment of small-scale field camps including a small power generator.

The intermixed thermal and structural framework of cold firn, water-saturated firn and ice layers in Greenland's percolation zone can be challenging to penetrate with core drills. Here, we present our experiences using a hot water drill for research on the firn layer of the percolation zone. We built and deployed a lightweight and easily transportable system for drilling a transect of ~15 cm diameter boreholes through the full firn column thickness, to depths exceeding 100 m. An instrumented drill stem provides a scientific measurement of the firn properties while drilling. The system was successful at gaining rapid access to the firn column with mixed wet and cold conditions, was easily transported to the site and across the glacier surface, and required a small field crew to operate. The boreholes are well suited for in situ investigations of firn processes in Greenland percolation zone.