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Abstract. Direct observations of the size of the Greenland Ice Sheet during Quaternary interglaciations are sparse yet valuable for testing numerical models of ice-sheet history and sea level contribution. Recent measurements of cosmogenicnuclides in bedrock from beneath the Greenland Ice Sheet collected duringpast deep-drilling campaigns reveal that the ice sheet was significantlysmaller, and perhaps largely absent, sometime during the past 1.1 millionyears. These discoveries from decades-old basal samples motivate new,targeted sampling for cosmogenic-nuclide analysis beneath the ice sheet.Current drills available for retrieving bed material from the US IceDrilling Program require < 700 m ice thickness and a frozen bed,while quartz-bearing bedrock lithologies are required for measuring a largesuite of cosmogenic nuclides. We find that these and other requirementsyield only ∼ 3.4 % of the Greenland Ice Sheet bed as asuitable drilling target using presently available technology. Additionalfactors related to scientific questions of interest are the following: which areas of thepresent ice sheet are the most sensitive to warming, where would a retreating icesheet expose bare ground rather than leave a remnant ice cap, andwhich areas are most likely to remain frozen bedded throughout glacialcycles and thus best preserve cosmogenic nuclides? Here we identifylocations beneath the Greenland Ice Sheet that are best suited for potentialfuture drilling and analysis. These include sites bordering Inglefield Landin northwestern Greenland, near Victoria Fjord and Mylius-Erichsen Land innorthern Greenland, and inland from the alpine topography along the icemargin in eastern and northeastern Greenland. Results from cosmogenic-nuclide analysis in new sub-ice bedrock cores from these areas would help to constrain dimensions of the Greenland Ice Sheet in the past. 

Abstract A new drilling system was developed by the US Ice Drilling Program (IDP) to rapidly drill through overlying ice to collect subglacial rock cores. The Agile Sub-Ice Geological (ASIG) Drill system is capable of drilling up to 700 m of ice in a continuous manner. Intermittent ice core samples can be taken as needed. Ten-plus meters of subglacial bedrock and unconsolidated, frozen sediment cores can be drilled with wireline core retrieval. The functionality of the drill system was demonstrated in 2016–17 at the Pirrit Hills, Antarctica where 8 m of high-quality, continuous granite core was retrieved beneath 150 m of ice. The particulars of the drill system development, features and performance are discussed. 

Abstract 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. 

Abstract 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. 

Abstract Over the course of the 2014/15 and 2015/16 austral summer seasons, the South Pole Ice Core project recovered a 1751 m deep ice core at the South Pole. This core provided a high-resolution record of paleoclimate conditions in East Antarctica during the Holocene and late Pleistocene. The drilling and core processing were completed using the new US Intermediate Depth Drill system, which was designed and built by the US Ice Drilling Program at the University of Wisconsin–Madison. In this paper, we present and discuss the setup, operation, and performance of the drill system.