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The need for scientific ice drilling in glaciers and ice sheets has been driven by many fields of science, including drilling ice cores for evidence of past environment and paleoclimate information, and drilling access holes through the ice to gather data relevant to glacial dynamics, history of glacier extent, sediment sampling, and discovery of ecosystems within and beneath the ice. Many nations have contributed to drilling technologies relevant to each of these fields, and developments in any one nation often build on prior designs from other nations. A description of the very early polar ice coring endeavors in Greenland and Antarctica is provided in Langway (2008). Ice drilling and coring technologies that were developed before 2008 are well described in Bentley et al (2009), including a wide array of ice coring drills, drills designed to create holes in ice only, and autonomous instruments that melt their way through ice. The text by [Talalay 2016] provides a review of mechanical ice drilling technology that includes design, parameters and performance of an assortment of tools and drills for making holes in snow, firn and ice. Described in detail are direct-push drilling, hand- and power-driven portable drills, percussion drills, conventional machine-driven rotary drill rigs, flexible drill-stem drill rigs, cable-suspended electromechanical auger drills, cable-suspended electromechanical drills with bottom-hole circulation, and drilling challenges and perspective for future development. In this chapter our goal is to describe new ice drilling and coring technologies that have been designed, built, and used in the field in the most recent decade. Some of these technologies are improvements on prior drills, while other technologies such as a replicate ice coring drill, geologic drilling underneath many meters of glacial ice, and the rapid access isotope drill are the first of their kind. There are many additional ice drilling and sampling designs currently in the design or development stage that are not included in this chapter; rather our goal in this chapter is to describe proven ice drilling technologies that have been developed since 2009. 

Abstract Thwaites Glacier represents 15% of the ice discharge from the West Antarctic Ice Sheet and influences a wider catchment 1–3 . Because it is grounded below sea level 4,5 , Thwaites Glacier is thought to be susceptible to runaway retreat triggered at the grounding line (GL) at which the glacier reaches the ocean 6,7 . Recent ice-flow acceleration 2,8 and retreat of the ice front 8–10 and GL 11,12 indicate that ice loss will continue. The relative impacts of mechanisms underlying recent retreat are however uncertain. Here we show sustained GL retreat from at least 2011 to 2020 and resolve mechanisms of ice-shelf melt at the submetre scale. Our conclusions are based on observations of the Thwaites Eastern Ice Shelf (TEIS) from an underwater vehicle, extending from the GL to 3 km oceanward and from the ice–ocean interface to the sea floor. These observations show a rough ice base above a sea floor sloping upward towards the GL and an ocean cavity in which the warmest water exceeds 2 °C above freezing. Data closest to the ice base show that enhanced melting occurs along sloped surfaces that initiate near the GL and evolve into steep-sided terraces. This pronounced melting along steep ice faces, including in crevasses, produces stratification that suppresses melt along flat interfaces. These data imply that slope-dependent melting sculpts the ice base and acts as an important response to ocean warming.