1) The first slide shows location maps of core drilling sites in Greenland and Antactica.
2) Slide 2 is a figure from Denton and Huges (1981) of the ice cover over the Northern Hemisphere during the maximum extent of the Wisconsin ice age at 18,000 years BP. At this time continental glaciers covered about 30% of the Earths land surface, today glacier ice covers about 12%.
3) Slide 3 lists the main sources of paleoenvironmental proxy data. Polar ice sheet chronologies are the most recently obtained and have furnished detailed climate and environmental records for up to 8,000 years BP. Samples of the ice from the deepest cores recovered to data, extend back to an estimated 125,000 to 200,000 years or more. It is interesting to note that it was only after the Camp Century ice core was augered to bedrock in 1996 that direct evidence verified the Greenland ice sheet was a remnant of the Wisconsin Ice age, and that the near bottom basil ice originated during the Sagamon(or Eem)interglacial some 100,000 plus years ago.
4a) At the top of slide 4, is a summary table listing some of the early studies conducted on glaciers. The ealiest drilling in ice is reported to have been in Switzerland at the margins of valley glaciers. They were augered to insert post holes for fences used to restrain domestic animals.
4b) Between 1895-1930 a number of exploratory traverses were made over the surface of Greenland and Antarctica by dog sled. Basic meteorological measurements and geographical feature were mapped, but a major occupation was trying to survive.
4c) From 1930-1940, with more mechanized forms of transportation and newscientific equipment, field research became more quantative. A rewarding example was the Alfred Wegener Expeditions to Greenland in the early 1930s. During these expeditions E. Sorge (1933,1935) developed a system to determine past snow accumulation using a deep-density relationship. Other geophysical experiments and seismic soundings were also performed.
4d) Between 1952-1954, Carl Benson, SIPRE made a systematic and comprehensive study of the distribution of snow accumulation over nearly the entire surface of the Greenland ice sheet. He used a tracked vehicle for transportation and hand-excavated scores of pits. Benson's research resulted in the most detailed regional mass-balance study ever conducted. In some pits he collected snow samples from the pit walls for oxygen isotope measurements (S. Epstein, Cal. Tech). This research laid the foundation for using the oxygen isotope rations to determine annual accumulation cycles in the Site-2 ice core, and as a standard method for all ice cores recovered since then.
4e) The lower part of slides 4 lists three early drilling projects that were all conducted almost simultaneously around the world in 1950. Members of the Junean Ice Field Research Project (M. Miller, 1954) core drilled to about 100m into the temperate Taku Glacier in Alaska; members of Expeditions Polaires Francaises (Henberger, 1954) augered two cores from the south central Greenland ice sheet to depths of 126m and 150m, and members of the British Norwegian Antarctic Expedition (DNSAE) cored to a depth of nearly 100m on the shelf ice along the Queen Maud I and Coast.
