page_title: Ice core
section_title: Early years
hierarchical_section_title: Ice core / History / Early years
caption_attribution_description: Geological core repository for sediment samples (POLARSTERN core repository, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven)
context_page_description: An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers or powered drills; they can reach depths of over two miles, and contain ice up to 800,000 years old.
  The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures, and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. These data can be combined to find the climate model that best fits all the available data.
  Impurities in ice cores may depend on location. Coastal areas are more likely to include material of marine origin, such as sea salt ions.
context_section_description: 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 m.  On Erich von Drygalski's Antarctic expedition in 1902 and 1903, 30 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 m long.  Similar devices are in use today, modified to allow sampling to a depth of about 9 m.  They are simply pushed into the snow and rotated by hand.
  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 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.  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.
  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.  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.  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.  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.
  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.
caption: A store of core samples
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