Wikipedia

User:Mike Christie/Sandbox11

< User:Mike Christie

Desor (1844) covers Agassiz's trips to the Aar glacier.

  • 1839 pp 127-140 they visit and walk along it but do no drilling
  • 1840 pp 141-? Agassiz had a 25 foot long drill made to allow him to take temperature measurements. (p. 142) p. 157 makes it clear we're still talking about 1840. p. 159 they try drilling (6 August, I think) and only get six inches penetration after several hours. Then it rains abundantly overnight and the next day they are astonished to find that they can penetrate more than a foot in less than fifteen minutes. They get to 20 feet (p.160). Then the next day they drill another hole that reaches 8 feet, a few steps away. They found that at a depth of eight or nine feet, the borehole temperature was constant, at -0.3 degrees. (still p. 160.)
  • 1841 starts p. 243 (winter)
  • 1841 spring starts p. 290. P. 292: Desor says they get to a depth of 140 feet that year (42.6 metres). P. 293, M. Koehli gives Desor a drill that is 150 feet long and is the same used for drilling artisanal (artesian?) wells; Koehli says a longer drill could not be used by hand and would require a scaffold, which would be too expensive to build. It was in ten fifteen-foot lengths, with cutting edges. 295: they start drilling and find that filling the hole with water causes the chips of ice from the bottom to float to the surface where they can be removed. At 70 feet depth the drill is too heavy. So they build a tripod and pulley, making it a cable tool. P/ 296-297 they have to restart drilling because the delay in building the tripod has caused the hole to close up. At 110 feet on the new hole they hit a pocket of air that causes the drill to drop two feet. Every day they took multiple temperature measurements, some in the deeper holes and some in shallower holes drilled just for that purpose; the measurements were taken at 15 feet depth. Later they reach 140 feet in the big hole. (p. 299). It sounds like nothing was deeper than 30 feet except the closed-up 70 foot hole and the 140 foot hole.
  • 1842 starts p. 491. Drilling starts 25 July. They are trying to determine the depth of the glacier. They get to 13m the first day. Problems including breaking equipment, and one day the workers left the drill in the hole, where it froze in; they took three days to extract it. Another time the hole "tordu" twisted in the night and they eventually decided to redrill in that hole. During the first three days, four men drilled about 13 meters. Once it was the backstage that broke, which forced to interrupt the work for several days to repair it. It was the hole that had twisted during the night. They will deliberate on the course of action. Would we start another hole or would we try to use the first one? They began again to drill with a crown three inches in diameter. In the meantime, the piercer became ever heavier, as we advanced; they were obliged to increase the number of the workmen to eight, and still only drilled three, and when the result was very favorable, four meters a day. They became convinced it was impossible to reach the base of the glacier with the means at their disposal. One day, when we measured the depth of a well or mill located in the middle of the Finsteraar glacier, half a league upstream from the Hotel des Neuchatelois, we came to our surprise that a stone, of probe, descended with increasing speed to the depth of 232 meters. We repeated these surveys several times, and we obtained nearly the same results. In the same way I measured a second hole, not far from the first, and found it nearly 150 meters deep. It is true that such measures can not be considered as rigorous, because of the obstacles which may stop the probe on the way. In these cases, it is to the tact of the experimenter that we must rely. However, we are all the more inclined to consider these soundings as accurate, which are confirmed by the fall of the stones in the same holes. It was thus reached mid-August, and foresaw that in no case could the depth be indicated by these drill holes, M. Agassiz decided that drilling should not be carried out more than 65 meters (200 feet) . They confined themselves to drilling a hole 32.5 metres (100 feet) and another of 16 metres, to serve for temperature observations.

Mercanton 1905:

p. 374: In 1840 nothing is deeper than 7 m. Looks like this is his conversion of 20 feet, or maybe 25 feet. GT gives "It should be borne in mind that in 1840 the mode of attack by running-in was hardly known and had only been applied to the excavation of mine holes in soft rock. The threshing was of almost exclusive use.The first attempts of Agassiz. made in 1840, by means of an ordinary miner's drill and a four-toothed rod, maneuvers by two men, had made it possible to arrive only at 7 m. at most, but had demonstrated the good effects of the presence of water in the borehole. So all subsequent drilling was carried out by holding the holes full of water.In 1841, Agassiz set to work with an artesian well probe. Its tooling included a 48-meter drill. long, with a full stem of 3 cm. of thickness, consisting of 1 segments placed end to end, plus a set of bits of various widths and a crown, tool in reversed funnel with wavy edge and sharp suitable for the movable terrains. This crown worked well up to 13 m. of about a depth, and was replaced by a single-bevel drill." Threshing is percussion.

p. 375 GT: "Up to 23 m, the threshing had been carried out by hand, but the piercer gradually heavier, it became necessary to support it among rope passing over a pulley at the head of a wooden head. They were then beating by pulling on the rope to raise the probe, which was then dropped.

The mixing of the water caused by the threshing facilitated the arrival of ice screws on the surface and dispensed with raising the piercer to clean the hole.

Thus Agassiz drilled in a rather long time (its exact duration is not indicated) two holes one of 10 m. on 8 cm. of diameter, the other of 46 m. depth and with a diameter varying between 16 cm. at the surface and 8 cm. basically. It had not been without difficulty, moreover, that various accidents had temporarily halted the work, among others the spontaneous contraction of the hole which Agassiz caused every evening to be emptied, in order to lower his thermometrographs.

In 1842, the work was resumed by the so-called "à la corde" sounding method or Chinese sounding. The tool, a long drill bit, was suspended from a rope passing over the pulley of the head-pipe, and the drill bit was beaten, and then dropped from its own weight. Desor's description was too rough, the apparatus was completed by a fixed rod guiding the rope and by a slide integral with the drill bit and sliding on the guide rod The tool was first the drill bit already tested and then a drill bit with single bevel.

This third survey campaign was marked by various accidents, which greatly slowed down the work and sometimes even destroyed the fruit of several days of effort."

p. 376. GT "One morning, stuck in the hole, was found the pier which the workmen had neglected to climb up the day before, and they lost three days in disengaging it. Another time it was found that the hole had become distorted during the night and refused to enter the pier. Above all, the advancement was a discouraging slowness. During the first 3 days, 4 men had made 13 m. daily; later it took 8 workers and still they did only 3 m, 4 m. maximum per day. The survey had to be stopped at a depth of 65 m. ; the hole was 8 cm. of diameter. Two other holes, 32.5 m. and 16 m. were still drilled and the glacial soundings finally abandoned after 6 weeks of incessant efforts.

Though they have been only half successful, the attempts of Agassiz and his companions are nevertheless of the greatest interest to the glacier, preoccupied with similar researches. They made known the hindrances that the temperature of the glacier and its movement can bring to work. They have demonstrated the urgent need for rapid advancement and highlighted the crucial role of water in achieving it. Last but not least, by making clear the insufficiency of the methods of attack by threshing, they have oriented the researchers made cautious and timorous may be, even in a very different way: the combined and continuous survey and cleansing of which I will speak now."

History

edit
 
A store of core samples

Early years

edit

The earliest attempt to drill through ice for scientific reasons was made by Louis Agassiz in 1840, on the Unteraargletscher in the Alps.[1] It was not clear to the scientific community of the day that glaciers flowed,[1] and when 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.[2] Agassiz spent part of 1840 on the glacier, and drilled several holes, none reaching more than 7 m deep, using a metal rod with a cutting tip.[1] 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, so Agassiz set up a line of flow markers on the glacier, intending to track their movement the following year.[1] In Glasgow that September Agassiz met James Forbes, who was interested in Agassiz's work on glaciers, and Agassiz invited him to join him the following summer on the Unteraargletscher.[3] When they arrived at the glacier in August 1841, so much snow had melted that the flow markers 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 in the ice was still embedded, with seven feet projecting above the surface, and ten feet showing by the start of September. Agassiz drilled deeper holes in 1841, and planted six stakes in a straight line, taking measurements with reference to identifiable points on the surrounding mountains to ensure that he would be able to tell if they had moved.[4] He also attempted to drill deeply enough to ascertain the thickness of the glacier, but found no bottom at 45 metres.[5]

The deepest hole achieved was 60 m. Another early scientific use for ice drilling was on Erich von Drygalski's Antarctic expedition; 30 m holes were drilled in an iceberg south of the Kerguelen Islands in 1902 and 1903, and temperature readings were taken. The first scientist to create a snow sampling tool was J.E. Church, described by Pavel Talalay as "the father of modern snow surveying". In the winter of 1908–1909, Church constructed steel tubes with slots and cutting heads to retrieve cores of snow up to 3 m long. Similar devices are in use today, with modifications that allow samples to a depth of about 9 m to be obtained. These tools are used by simply pushing them into the snow and rotating them by hand.[6]

The first systematic study of snow and firn layers was by Ernst Sorge, who was part of the Alfred Wegener Expedition to central Greenland in 1930–1931. Sorge dug a 15 m deep pit to examine the snow layers, and his results were later formalized into Sorge's Law of Densification by Henri Bader, who went on to do additional coring work in northwest Greenland in 1933.[7] In the early 1950s, a SIPRE expedition obtained pit samples over much of the Greenland ice sheet, obtaining early oxygen isotope ratio data. Three other expeditions in the 1950s began ice coring work: a joint Norwegian-British-Swedish Antarctic Expedition (NBSAE), in Queen Maud Land in Antarctica; the Juneau Ice Field Research Project (JIRP), in Alaska; and Expéditions Polaires Françaises, in central Greenland. Core quality was poor, but some scientific work was done on the retrieved ice.[8]

The International Geophysical Year (1957–1958) saw increased glaciology research around the world, with deep cores in polar regions one of the high priority research targets. SIPRE conducted pilot drilling trials in 1956 (to 305 m) and 1957 (to 411 m) at Site 2 in Greenland; the second core, with the benefit of the previous year's drilling experience, was retrieved in much better condition, with fewer gaps.[9] In Antarctica, a 307 m core was drilled at Byrd Station in 1957–1958, and a 264 m core at Little America V, on the Ross Ice Shelf, the following year.[10] The success of the IGY core drilling led to increased interest in improving ice coring capabilities, and was followed by a CRREL project at Camp Century, where in the early 1960s three holes were drilled, the deepest reaching the base of the ice sheet at 1387 m in July 1966.[11] The drill used at Camp Century then went to Byrd Station, where a 2164 m hole was drilled to bedrock before the drill was frozen into the borehole by sub-ice meltwater, and had to be abandoned.[12]

French, Australian and Canadian projects from the 1960s and 1970s include a 905 m core at Dome C in Antarctica, drilled by CNRS; cores at Law Dome drilled by ANARE, starting in 1969 with a 382 m core; and Devon Ice Cap cores recovered by a Canadian team in the 1970s.[13]

Antarctica deep cores

edit
 
Composite data for Dome C, CO2 levels (ppm) going back nearly 800,000 years, and related glacial cycles.

Soviet ice drilling projects began in the 1950s, in Franz Josef Land, the Urals, Novaya Zemlya, and at Mirny and Vostok in the Antarctic; not all these early holes retrieved cores.[14] Over the following decades work continued at multiple locations in Asia.[15] Drilling in the Antarctic focused mostly on Mirny and Vostok, with a series of deep holes at Vostok begun in 1970.[16] The first deep hole at Vostok reached 506.9 m in April 1970; by 1973 a depth of 952 m had been reached. A subsequent hole, Vostok 2, drilled from 1971 to 1976, reached 450 m, and Vostok 3 reached 2202 m in 1985 after six drilling seasons.[17] Vostok 3 was the first core to retrieve ice from the previous glacial period, 150,000 years ago.[18] Drilling was interrupted by a fire at the camp in 1982, but further drilling began in 1984, eventually reaching 2546 m in 1989. A fifth Vostok core was begun in 1990, reached 3661 m in 2007, and was later extended to 3769 m.[13][18] The estimated age of the ice is 420,000 years at 3310 m depth; below that point it is difficult to interpret the data reliably because of mixing of the ice.[19]

 
The EPICA Dome C and Vostok ice cores compared

EPICA, a European ice coring collaboration, was formed in the 1990s, and two holes were drilled in East Antarctica: one at Dome C, which reached 2871 m in only two seasons of drilling, but which took another four years to reach bedrock at 3260 m; and one at Kohnen Station, which reached bedrock at 2760 m in 2006. The Dome C core had very low accumulation rates, which mean that the climate record extended a long way; by the end of the project the usable data extended to 800,000 years ago.[19]

Other deep Antarctic cores included a Japanese project at Dome F, which reached 2503 m in 1996, with an estimated age of 330,000 years for the bottom of the core; and a subsequent hole at the same site which reached 3035 m in 2006, estimated to reach ice 720,000 years old.[19] US teams drilled at McMurdo Station in the 1990s, and at Taylor Dome (554 m in 1994) and Siple Dome (1004 m in 1999), with both cores reaching ice from the last glacial period.[19][20] The West Antarctic Ice Sheet (WAIS) project, completed in 2011, reached 3405 m; the site has high snow accumulation so the ice only extends back 62,000 years, but as a consequence, the core provides high resolution data for the period it covers.[21] A 948 m core was drilled at Berkner Island by a project managed by the British Antarctic Survey from 2002 to 2005, extending into the last glacial period;[21] and an Italian-managed ITASE project completed a 1620 m core at Talos Dome in 2007.[21][22]

In 2016, cores were retrieved from the Allan Hills in Antarctica in an area where old ice lay near the surface. The cores were dated by potassium-argon dating; traditional ice core dating is not possible as not all layers were present. The oldest core was found to include ice from 2.7 million years ago—by far the oldest ice yet dated from a core.[23]

Greenland deep cores

edit

In 1970, scientific discussions began which resulted in the Greenland Ice Sheet Project (GISP), a multinational investigation into the Greenland ice sheet that lasted until 1981. Years of field work were required to determine the ideal location for a deep core; the field work included several intermediate-depth cores, at Dye 3 (372 m in 1971), Milcent (398 m in 1973) and Crete (405 m in 1974), among others. A location in north-central Greenland was selected as ideal, but financial constraints forced the group to drill at Dye 3 instead, beginning in 1979. The hole reached bedrock at 2037 m, in 1981. Two holes, 30 km apart, were eventually drilled at the north-central location in the early 1990s by two groups: GRIP, a European consortium, and GISP-2, a group of US universities. GRIP reached bedrock at 3029 m in 1992, and GISP-2 reached bedrock at 3053 m the following year.[24] Both cores were limited to about 100,000 years of climatic information, and since this was thought to be connected to the topography of the rock underlying the ice sheet at the drill sites, a new site was selected 200 km north of GRIP, and a new project, NorthGRIP, was launched as an international consortium led by Denmark. Drilling began in 1996; the first hole had to be abandoned at 1400 m in 1997, and a new hole was begun in 1999, reaching 3085 m in 2003. The hole did not reach bedrock, but terminated at a subglacial river. The core provided climatic data back to 123,000 years ago, which covered part of the last interglacial period. The subsequent North Greenland Eemian (NEEM) project retrieved a 2537 m core in 2010 from a site further north, extending the climatic record to 128,500 years ago;[18] NEEM was followed by EastGRIP, which began in 2015 in east Greenland and is expected to be complete in 2020.[25]

Non-polar cores

edit

Ice cores have been drilled at locations away from the poles, notably in the Himalayas and the Andes. Some of these cores reach back to the last glacial period, but they are more important as records of El Niño events and of monsoon seasons in south Asia.[21] Cores have also been drilled on Mount Kilimanjaro,[21] in the Alps,[21] and in Indonesia,[26] New Zealand,[27] Iceland,[28] Scandinavia,[29] Canada,[30] and the US.[31]

References

edit
  1. ^ a b c d Clarke (1987), p. 4.
  2. ^ Agassiz (1866), pp. 295–296.
  3. ^ Marcou (1905), pp. 187–188.
  4. ^ Agassiz (1866), p. 297.
  5. ^ Agassi (1847), p. 87.
  6. ^ Talalay (2016), pp. 9–11.
  7. ^ Langway (2008), pp. 5–6.
  8. ^ Langway (2008), p. 7.
  9. ^ Langway (2008), pp. 9–11.
  10. ^ Langway (2008), pp. 14–15.
  11. ^ Langway (2008), pp. 17–20.
  12. ^ Langway (2008), p. 23.
  13. ^ a b Jouzel (2013), p. 2527.
  14. ^ Ueda & Talalay (2007), pp. 3–5.
  15. ^ Ueda & Talalay (2007), pp. 50–58.
  16. ^ Ueda & Talalay (2007), pp. 3–26.
  17. ^ Ueda & Talalay (2007), p. 11.
  18. ^ a b c Jouzel (2013), p. 2528.
  19. ^ a b c d Jouzel (2013), p. 2529.
  20. ^ Bentley & Koci (2007), pp. 3–4.
  21. ^ a b c d e f Jouzel (2013), p. 2530.
  22. ^ Iaccarino, Tony. "TALos Dome Ice CorE – TALDICE". Talos Dome Ice Core. Retrieved 28 May 2017.
  23. ^ "Record-shattering 2.7-million-year-old ice core reveals start of the ice ages". Science | AAAS. 2017-08-14. Retrieved 2017-08-30.
  24. ^ Langway (2008), pp. 27–28.
  25. ^ Madsen, Martin Vindbæk (15 March 2016). "Documentation". eastgrip.org. Retrieved 17 March 2017.
  26. ^ MacKinnon (1980), p. 41.
  27. ^ MacKinnon (1980), p. 42.
  28. ^ MacKinnon (1980), p. 36.
  29. ^ MacKinnon (1980), p. 39.
  30. ^ MacKinnon (1980), p. 26-29.
  31. ^ MacKinnon (1980), p. 30.

Sources

edit
Retrieved from "https://en.wikipedia.org/w/index.php?title=User:Mike_Christie/Sandbox11&oldid=1092267759"