Greenland Ice Sheet Project (GISP)
The Greenland Ice Sheet Project (GISP) was a decade-long project to drill 20 ice cores in Greenland. GISP involved scientists and funding agencies from Denmark, Switzerland and the United States. Besides the U.S. National Science Foundation, funding was provided by the Swiss National Science Foundation and the Danish Commission for Scientific Research in Greenland. The ice cores provide a proxy archive of temperature and atmospheric constituents that help to understand past climate variations.
Annual field expeditions were carried out to drill intermediate depth cores at various locations on the ice sheet:
- Dye 3 in 1971 to 372 m
- North Site (75°46’N 42°27’W, 2870 masl) in 1972 to 15 m
- North Central (74°37’N 39°36’W) in 1972 to 100 m
- Crête (71°7’N 37°19’W) in 1972 to 15 m
- Milcent (70°18’N 45°35’W, 2410 masl) in 1973 to 398 m
- Dye 2 (66°23’N 46°11’W) in 1973 to 50 m
- Dye 3 in 1973, an intermediate drilling to c. 390 m
- Crête in 1974 to 404.64 m
- Dye 2 in 1974 to 101 m
- Summit (71°17’N 37°56’W, 3212 masl) in 1974 to 31 m
- Dye 3 in 1975 to 95 m
- South Dome (63°33’N 44°36’W, 2850 masl) in 1975 to 80 m
- Hans Tausen (82°30’N 38°20’W, 1270 masl) in 1975 to 60 m
- Dye 3 in 1976 to 93 m
- Hans Tausen in 1976 to 50 m
- Hans Tausen in 1977 to 325 m
- Camp Century (77°10’N 61°8’W, 1885 masl) in 1977 to 49 m
- Dye 2 in 1977 to 84 m
- Camp III (69°43’N 50°8’W) in 1977 to 84 m
- Dye 3 1978 to 90 m
- Camp III in 1978 to 80 m.
“On most of the Greenland ice sheet, however, the annual accumulation rate is considerably higher than 0.2 m ice a-1, and the delta method therefore works thousands of years backwards in time, the only limitation being obliteration of the annual delta cycles by diffusion of the water molecule in the solid ice....” Delta refers to the changing proportion of oxygen-18 in the different seasonal layers. “The main reason for the seasonal delta variations is that, on its travel to the polar regions, a precipitating air mass is generally cooled more in winter than in summer.” “... the annual layer thickness...decreases from 19 cm in 2,000-yr-old ice to 2 cm in 10,000-yr-old ice due to plastic thinning of the annual layers as they sink towards greater depths10.” “... volcanic acids in snow layers deposited shortly after a large volcanic eruption can be detected - as elevated specific conductivities measured on melted ice samples8, or as elevated acidities revealed by an electric current through the solid ice...”
Read more about this topic: Dye 3
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