Scientific ice drilling began in 1840, when Louis Agassiz attempted to drill through the Unteraargletscher in the Alps. Rotary drills were first used to drill in ice in the 1890s, and thermal drilling, with a heated drillhead, began to be used in the 1940s. Ice coring began in the 1950s, with the International Geophysical Year at the end of the decade bringing increased ice drilling activity. In 1966, the Greenland ice sheet was penetrated for the first time with a 1,388 m hole reaching bedrock, using a combination of thermal and electromechanical drilling. Major projects over the following decades brought cores from deep holes in the Greenland and Antarctic ice sheets.
Hand drilling, using ice augers to retrieve small cores, or small drills using steam or hot water to install ablation stakes, is also common.
History Agassiz
The earliest attempt to drill through ice for scientific reasons was made by Louis Agassiz in 1840, on the Unteraargletscher in the Alps.Clarke (1987), p. 4. It was not clear to the scientific community of the day that glaciers flowed, and when Franz Josef Hugi demonstrated that a large boulder on the Unteraargletscher had moved 1315 m between 1827 and 1836, sceptics argued that the boulder might have slid down the glacier.Agassiz (1866), pp. 295–296. Agassiz visited the glacier in 1839,Desor (1844), pp. 127–140. and returned in the summer of 1840. He planned to make temperature observations on the glacier's interior, and brought an iron drilling rod, long, for that purpose.Desor (1844), pp. 141–142. The first attempt at drilling, in early August, made only of progress after several hours work. After heavy rain overnight, the drilling became much faster: a foot (30 cm) of progress was made in less than fifteen minutes, and the hole eventually reached a depth of . Another hole drilled nearby reached ,Desor (1844), pp. 159–160. and more were drilled to place six flow markers in a line across the glacier, which Agassiz hoped would have moved by the following year, demonstrating the flow of the glacier. He believed in the dilatation theory of glacier flow, which argued that the refreezing of meltwater caused glaciers to progressively lengthen; this theory implied that the flow rate should be greatest where the water input was greatest.
Agassiz returned to the Unteraargletscher in August 1841, this time equipped with a drill consisting of 10 iron rods, each long, of the kind used to drill for wells; a longer drill could not have been used by hand, and would have required a scaffold, which would have been too expensive. He was hoping to drill deeply enough to ascertain the thickness of the glacier. Once it was realized that drilling went faster when the holes were full of water, the holes were positioned so that they could be supplied with water by one of the many small streams on the glacier. This had the additional benefit of simplifying the removal of the chips of ice from the bottom of the hole, as they rose to the surface and were carried away by the current. When the first hole reached the drilling rods became too heavy for the men to use, so a tripod was constructed and a pulley set up so the drill could be raised and lowered by a cable. The tripod took several days to complete, and when the men attempted to begin drilling again they were surprised to discovered the drill would no longer go into the hole, which had closed up to only half an inch across, forcing them to start a new hole. The deepest hole achieved in 1841 was .Desor (1844), pp. 292–299.
The flow markers placed in 1840 were located in 1841 but proved to be uninformative; so much snow had melted that they were all lying flat on the glacier, which made them useless for proving the movement of the ice they had been embedded in. However, a stake set eighteen feet deep in the ice was still embedded, with seven feet projecting above the surface, and ten feet showing by the start of September 1841. Agassiz drilled deeper holes, and planted six stakes in a straight line across the glacier, taking measurements with reference to identifiable points on the surrounding mountains to ensure that he would be able to tell if they had moved.Agassiz (1866), pp. 296–297.Agassi (1847), p. 87.
These flow markers were still in place in July 1842 when Agassiz returned to the Unteraargletscher, and now formed a crescent shape; it was apparent that the ice flowed much faster in the centre of the glacier than at the edges. Drilling began again on 25 July, again using the cable tool approach. Some problems were encountered: the equipment broke at one point and had to be repaired; and on one occasion it was discovered that the borehole had become distorted overnight, and had to be redrilled. As the hole became deeper, the increasing weight of the drilling equipment forced Agassiz to increase the number of men pulling on the cable to eight; even so they only were able to gain three or four metres a day. While the drilling continued, soundings were taken of moulins and depths of 232 m and nearly 150 m were found. Although Agassiz understood that these measurements were not rigorous, because unseen obstacles might be distorting the readings, he became convinced that it would be impossible for his team to drill to the base of the glacier, and it was decided not to drill below . Additional holes were subsequently drilled to 32.5 m and 16 m to be used for temperature measurements.Desor (1844), pp. 491–494.
Late 19th century
Blümcke and Hess Agassiz's demonstration of the great difficulty of drilling deep holes in glacier ice discouraged other researchers from further efforts in this direction. It was decades before further advances were made in the field, but two patents, the first ice-drilling related ones to be issued, were registered in the United States in the late 19th century: in 1873, W.A. Clark received a patent for his "Improvement in Ice-Augers", which allowed the size of the hole to be specified, and in 1883, R. Fitzgerald patented a hand-powered drill made from a cylinder with cutting blades attached to the bottom.Talalay (2016), p. 9.
Between 1891 and 1893 Erich von Drygalski visited west Greenland on two expeditions, and drilled shallow holes there with a spoon-borer: a hollow steel cylinder 75 cm long with a pair of angled blades at the bottom; for holes deeper than 75 cm, additional tubes of the same length could be added. Ice cut by the blades was captured in the cylinder, which would be periodically pulled up to empty out the ice cuttings. The holes were drilled to measure ice movement by placing poles (mostly bamboo) in them and monitoring them. The greatest depth achieved was only 2.25 m, but von Drygalski commented that deeper holes would have been easy to drill; a 1.5 m hole in 0° temperature took about 20 minutes. Von Drygalski took other drill designs, but found the spoon-borer to be the most effective.Von Drygalski (1897), pp. 170–171.
In 1894 Adolf Blümcke and Hans Hess began a series of expeditions to the Hintereisferner. As no ice drilling to any depth had been attempted since Agassiz's expedition, they had no recent examples to learn from, so they experimented in the winter of 1893–1894 with drill designs in the ice cellar of a brewery. From the start they decided against percussion drilling, and they examined one of the drills von Drygalski had taken to Greenland as part of their testing. They also built a copy of von Drygalski's spoon-borer but found it too weak to retain its shape in use. They used a hand crank to rotate the drillbit, which was a helical auger. Their original plan was remove the ice cuttings by bailing, but they almost immediately abandoned this plan;Blümcke & Hess (1899), pp. 33–34. instead, the auger was removed from the borehole at intervals, and a tube inserted to pump water down the hole to carry away the cuttings. This was an entirely new approach, and some trial and error was required to perfect the method. A depth of 40 m was achieved.Flusin & Bernard (1909), pp. 7–8.Mercanton (1905), p. 452-453. The following year they modified the auger so water could be pumped down the drillstring itself, emerging from a hole in the auger, and carrying the cuttings back up around the outside of the drill; this eliminated the need to remove the drill to clear the cuttings. Only about seven hours a day could be used for drilling since there was no flowing water on the glacier overnight.Blümcke & Hess (1899), pp. 34–35.
The drill frequently became wedged in the ice, perhaps because the borehole had deformed, and it was also common to encounter rocks in the ice, which could be identified by rock splinters that were carried up to the surface in the water that cleared the ice cuttings. The most troublesome problem was drilling into voids in the ice. At the bottom of the void a new borehole would be started; if the cavity was such that the water pumped through the drillpipe could flow away from the borehole once it was forced back up around the pipe, then drilling could continue; if not, the cuttings would accumulate around the borehole and eventually further progress would become impossible. Blümcke and Hess attempted to run casing pipe down through the cavity, so that the water and cuttings could continue to come up to the surface, but this was unsuccessful, and would have been too expensive a solution to implement every time the problem occurred.Mercanton (1905), pp. 457–459.
In 1899 the bed of the glacier was reached in two places, with depths of 66 m and 85 m, and this success persuaded the German and Austrian Alpine Club, which had subsidized the early expeditions, to fund ongoing work and build an improved version of the drilling apparatus, which became available in 1901. A key improvement was adding lateral cutting edges to the auger, enabling it to recut the hole and avoid wedging if it was reinserted into a hole that had become deformed. The equipment weighed 4000 kg, which along with the cost of transport in the high mountains, and the need to employ a large team, made their method expensive,Bourgin (1950), p. 625. though Blümcke and Hess suggested that their approach would not be too costly for other teams to reproduce.Blümcke & Hess (1910), pp. 66–70. In a review of Blümcke and Hess's work published in 1905, Paul Mercanton suggested that a petrol engine to power both the rotation of the drill and the water pump would be natural improvements. It had been noticed that the pump work became much more difficult with depth, and up to eight men were needed to continue pumping for the very deepest holes. Mercanton also noticed that whereas Blümcke and Hess's drill required about 60 litres per minute to clear the cuttings, a similar drill he had worked on with Constant Dutoit required only 5% as much water for the same purpose, and he suggested that placing the outflow of water at the very bottom of the drill bit was the key to reducing conflicting water flows around the drill bit and reducing the need for water.Mercanton (1905), pp. 463–464.
The holes were drilled to verify calculations Blümcke and Hess had made of the glacier's form and expected depth, and the results were in quite good agreement with their expectations. In total Blümcke and Hess completed 11 holes to the glacier bed between 1895 and 1909, and drilled many more holes that did not penetrate the glacier. The deepest hole they drilled was 224 m.Clarke (1987), p. 11–12.
Vallot, Dutoit, and Mercanton