Editing Ice core (section)

=== Early years ===
[[File:2000 core-repository02 hg.jpg|thumb|A store of core samples|alt=A man on a walkway between two high shelf racks loaded with ice core samples]]

In 1841 and 1842, [[Louis Agassiz]] drilled holes in the [[Unteraargletscher]] in the [[Alps]]; these were drilled with iron rods and did not produce cores.  The deepest hole achieved was 60&nbsp;m.  On [[Erich von Drygalski]]'s Antarctic expedition in 1902 and 1903, 30&nbsp;m holes were drilled in an iceberg south of the Kerguelen Islands and temperature readings were taken.  The first scientist to create a snow sampling tool was [[James 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&nbsp;m long.  Similar devices are in use today, modified to allow sampling to a depth of about 9&nbsp;m.  They are simply pushed into the snow and rotated by hand.<ref>{{harvnb|Talalay|2016}}, pp. 9–11.</ref>

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&nbsp;m 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.<ref>{{harvnb|Langway|2008}}, pp. 5–6.</ref> In the early 1950s, a [[SIPRE]] expedition took 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.<ref>{{harvnb|Langway|2008}}, p. 7.</ref>

The [[International Geophysical Year]] (1957–1958) saw increased [[glaciology]] research around the world, with one of the high priority research targets being deep cores in polar regions.  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.<ref>{{harvnb|Langway|2008}}, pp. 9–11.</ref> In Antarctica, a 307&nbsp;m core was drilled at [[Byrd Station]] in 1957–1958, and a 264&nbsp;m core at [[Little America V]], on the [[Ross Ice Shelf]], the following year.<ref>{{harvnb|Langway|2008}}, pp. 14–15.</ref> 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&nbsp;m in July 1966.<ref>{{harvnb|Langway|2008}}, pp. 17–20.</ref> The drill used at Camp Century then went to Byrd Station, where a 2164&nbsp;m hole was drilled to bedrock before the drill was frozen into the borehole by sub-ice meltwater and had to be abandoned.<ref>{{harvnb|Langway|2008}}, p. 23.</ref>

French, Australian and Canadian projects from the 1960s and 1970s include a 905&nbsp;m core at [[Dome C]] in Antarctica, drilled by [[Centre national de la recherche scientifique|CNRS]]; cores at [[Law Dome]] drilled by [[Australian National Antarctic Research Expeditions|ANARE]], starting in 1969 with a 382&nbsp;m core; and [[Devon Ice Cap]] cores recovered by a Canadian team in the 1970s.<ref name="Jouzel-2013-1" />