page_title: Dye 3
section_title: Visual stratigraphy
hierarchical_section_title: Dye 3 / Comparison with other Greenland ice cores / GISP2 1989 / Visual stratigraphy
context_page_description: Dye 3 is an ice core site and previously part of the Distant Early Warning line, located at in Greenland. As a DEW line base, it was disbanded in years 1990/1991.
  An ice core is a core sample from the accumulation of snow and ice that has re-crystallized and trapped air bubbles over many years. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time. Ice cores contain an abundance of climate information.
  Inclusions in the snow, such as wind-blown dust, ash, bubbles of atmospheric gas and radioactive substances, remain in the ice. The variety of climatic proxies is greater than in any other natural recorder of climate, such as tree rings or sediment layers. These include temperature, ocean volume, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity, desert extent and forest fires.
  Typical ice cores are removed from an ice sheet such as the ice cap internal to Greenland. Greenland is, by area, the world's largest island. The Greenland ice sheet covers about 1.71 million km² and contains about 2.6 million km³ of ice.
context_section_description: The GISP2 time scale is based on counting annual layers primarily by visual stratigraphy.
  The isotopic temperature records show 23 interstadial events correlateable between the GRIP and GISP2 records between 110 and 15 kyr B.P. Ice in both cores below 2790 m depth (records prior to 110 kyr B.P.) shows evidence of folding or tilting in structures too large to be fully observed in a single core.
  The bulk of the GISP2 ice core is archived at the National Ice Core Laboratory in Lakewood, Colorado, United States.
caption: 19 cm long section of GISP 2 ice core from 1855 m showing annual layer structure illuminated from below by a fiber optic source. Section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers.
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