Greenland Ice Sheet Project

The Greenland Ice Sheet Project (GISP) was a drilling program for the extraction of ice cores and the paleoclimatological data contained therein from the Greenland ice sheet . It was funded by the American National Science Foundation (NSF) and was one of the largest scientific projects of the NSF in the late 1970s and 1980s. GISP ran for more than ten years. The participating scientists came from Denmark , Switzerland and the United States of America . In addition to the NSF, the project was co-financed by the Swiss National Fund for the Promotion of Scientific Research and the Danish Commission for Scientific Investigations in Greenland ( Danish Commissions for Videnskabelige Undersøgelser i Grønland ).

GISP field work started in 1971 with the Dye-3 drilling . This 372 meter long core was 10.2 cm thick. After that, field expeditions were undertaken annually. In this way, drill cores could be retrieved from medium depths from different parts of the ice sheet. The first hole returned 392 meters of core at Milcent and another returned 405 meters of core in 1974 near Crete Station. Logistical and technical problems resulted in the development of a better derrick. In the summer of 1979, a well was started, which should lead to the bedrock of Dye 3. In the first year, a hole with a diameter of 18 cm was drilled and stripped to a depth of 80 m. The core drilling continued over two seasons; on August 10, 1981, the bedrock was reached at a depth of 2037 m.

The data obtained through GISP have contributed to a great increase in knowledge regarding the history of the Greenland Ice Sheet and the climate history of the earth. They have shown the importance of the climatic data preserved in ice sheets. For example, the researchers found that there were severe climatic fluctuations in Greenland during the last Ice Age, so-called Dansgaard-Oeschger events . Traces of the Heinrich events were also found.

GISP2

GISP2 ice core extracted from a depth of 1837 m with clearly recognizable annual stratification

Holocene temperature course in Central Greenland, according to data from GISP2

The GISP2 project began in 1989 . Ice cores with a length of 3000 m should provide climatic data for the last 200,000 years.

GISP2 was funded by the United States National Science Foundation Division of Polar Programs as part of the Arctic System Science Initiative (ARCSS). Scientists from the following institutes were involved in the GISP2 project:

• United States Army Cold Regions Research and Engineering Laboratory in Hanover , New Hampshire
• Carnegie Mellon University Desert Research Institute in Reno , Nevada
• Massachusetts Institute of Technology
• Ohio State University
• Pennsylvania State University
• New York State Department of Health
• State University of New York at Albany
• State University of New York at Buffalo
• Lamont-Doherty Geological Observatory of Columbia University
• University of Arizona
• University of Colorado
• University of Miami
• University of New Hampshire
• University of Rhode Island
• University of Washington
• United States Geological Survey in Tacoma , Washington
• University of Wisconsin

Drilling location

The GISP2 wells were drilled at the highest point of the Greenland Ice Sheet, at 73 °  N , 38 °  W at an altitude of 3208 m above sea level, on the western Greenland ice divide. At this point, ice flows off both west and east.

Technique of drilling

A 20 m high derrick was used for the drilling, along with special drill heads. The core was sawn into pieces of 2 and 6 m in length. When handling the drill cores, great care had to be taken to ensure that the drill core was not contaminated with foreign material; even touching it with the bare hand could have falsified the subsequent evaluation.
When the camp was closed on September 14, 1991, GISP2 had reached a depth of 1,510 m. The oldest ice parts of the drill core reached up to the year 8000 BC. BC back. On July 1, 1993, after drilling 3,053.44 m of ice and 1.55 m of stone, the longest ice core ever made was obtained.

evaluation

In addition to indirect temperature measurements using the δ ¹⁸ O signal , the concentrations of greenhouse gases such as carbon dioxide , methane and nitrous oxide are also examined. The carbon dioxide samples are not only examined for their absolute concentration, but the isotope concentration ¹⁴ C is also analyzed in order to obtain information on the origin of the carbon dioxide. Conductivity measurements are used to get a quick overview of past volcanic eruptions, as the changed acidity of the ice leads to a change in conductivity. If such an event is found, further details of the outbreak can be determined by analyzing the trapped dust particles (size, composition, amount). Measurements of the concentration of SO ₄ give indications of biological or volcanic activities, changes in the concentration of sulphates and NO ₃ indicate the burning of fossil fuels, as could be seen in the flat parts of Core3. The analysis of the concentration of iridium gives indications of meteorite impacts, since this material occurs preferentially in meteorites.

At around the same time, the neighboring European project GRIP took place 28 km away , which also drilled an ice core from a depth of more than 3000 m.

See also

• EPICA - (European Project for Ice Coring in Antarctica), a European project to carry out ice core drilling in the Antarctic

swell

• GISP info page from NOAA
• Homepage of the GISP2 project
• Info page on the homepage of the GISP2 project

Individual evidence

1. ↑ cf. RB Alley: The Younger Dryas cold interval as viewed from central Greenland . In: Quaternary Science Reviews . January 2000, doi : 10.1016 / S0277-3791 (99) 00062-1 .