The GRIP Ice Coring Effort


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Introduction

Within the framework of the joint European Greenland Ice Core Project (GRIP) a 3029 m long ice core was drilled in Central Greenland from 1989 to 1992 at 72o 35' N, 37o 38' W. Polar ice cores contain a record of tha past atmosphere - temperature, precipitation, gas content, chemical composition, and other properties. The objective of the GRIP effort was to reveal the broad spectrum of information on past environmental, and particularly climatic, changes that are stored in the ice. This information will help investigators understand the major mechanisms of the earth and man's potential impact.


K. Makinson
Studies of isotopes and various atmospheric constituents in the core have revealed a detailed record of climatic variations reaching more than 100,000 years back in time. The results indicate that Holocene climate has been remarkably stable and have confirmed the occurrence of rapid climatic variation during the last ice age (the Wisconsin). Climatic instability observed in the core part believed to date from the Eemian interglacial has not been confirmed by other climate records.

GRIP Drilling Effort

In the first drilling season in 1990, the drill reached a depth of 770m where the ice is 3840 years old. In 1991, the drilling continued into 40,000 year old ice at a depth of 2521m, and on 12 August 1992, the drill hit bedrock at 3029m below the surface, where the ice is 200,000 years old or more. The core is now stored in a cold house at the University of Copenhagen. The GRIP deep drill is an updated version of ISTUK (IS means ice in Danish, TUK means drill in Greenlander). ISTUK was constructed in 1978 and used successfully under the American-Danish-Swiss GISP 1 program at Dye 3 in South Greenland where it hit bedrock at a depth of 2037m in 1981.


K. Makinson
Although the actual drilling was completed in 1992, there was a last short field campaign in Greenland and at Summit to measure ice sheet strain parameters and to extend upward the GRIP hole so that detailed temperature and deformation measurements will still be possible. Using the experience accumulated through GRIP and the facilities of this last campaign, the successful development and testing of a special drill for the European Project for Ice Coring in Antarctica (EPICA) was also carried out. This new European drill will be able to operate in the much harsher environmental conditions to be found at Dome Concordia in Antarctica.

Dating the GRIP Core

It was possible to count annual layers in the GRIP core to obtain an excellent dating, particularly back to the Younger Dryas period. Parameters used to date the core included ECM, dust, nitrate and ammonium, which all give excellent annual layers, particularly in the Holocene period. Comparison with the previously dated Dye 3 core, using volcanic and other tie-points, provided a starting point. Numerous volcanic eruptions were documented, allowing the possibility to make comparisons with other cores. Deeper ice was dated using ice flow models.

Measurements Made on the GRIP Core

A huge number of analyses were made on the core in the field, while other samples were prepared in the field for shipment to laboratories around Europe. measurements in the field helped scientists to select samples for special and urgen analyses, and to exclude the contamination risk from chemicals such as organic acids.


Eric Wolff, GRIP Steering Committee and Management Group, British Antarctic Survey
Continuous measurements made in the field included dielectric profiling and electrical conductivity (related to the concentrations of neutral salts and acid). Thin sections were made in the field to examine crystal sizes and fabrics. Chemical measurements made continuously in the field were ammonium, nitrate, hydrogen peroxide, formaldehyde, calcium and dust, while discontinuous measurements of other anions and cations were made by ion-chromatography. Samples were cut in the field for oxygen isotope and deuterium analysis (with a resolution of about 3 cm in parts of the core), for trace gas analysis, for measurements of 10Be, and mechanical properties of the ice, among others.

Findings from the GRIP Core

The most dramatic finding from GRIP was that of the rapid climate changes (Dansgaard-Oeschger events) in the last glacial period. These had been observed in previous cores, but GRIP confirmed their existence, their number, and the extreme rapidity of their onset in unprecedented detail. Such work has stimulated paleoclimatologists in other fields to see how global these events are and to look for causes.

Among numerous other findings, new insights using markers of biological material have proved particularly exciting. Methane has been found to change in time with many rapid climate changes. Spikes of ammonium and organic acids have been found to be markers for biomass burning, while background concentrations of these species indicate the advances of vegetation in North America.

Measurements of borehole temperatures have allowed a re-calibration of the oxygen isotope-temperature relation for the GRIP ice core. This work indicates that the temperature chnage at the end of the last glacial period was more than 20 degrees, a result found independently in the GISP2 borehole. These increased temperature changes provide a renewed challenge to those seeking mechanisms for the transitions.


K. Makinson
The GRIP core offers a unique possibility to study the growth, rotation and recrystallization of polar ice at an ideal location, covering a time span of more than 100,000 years. This information is obtained by a comprehensive thin section study of crystal sizes and c-axis orientations along its entire length. The results confirm earlier, basic observations on deep ice cores and have led to new insights. A significant variation of crystal size with climatic parameters is shown to persist to a great depth in the core; the development of a strong crystalline anisotropy in the ice sheet is also demonstrated. Considerable insight is obtained into the rheological properties of the ice sheet from these studies.

More detailed findings are reported in a large number of papers listed in this CD-ROM, and in the GRIP final report, available also on this CD-ROM.

Acknowledgments

GRIP has been a multinational European research project, organized through the European Science Foundation (ESF). Funding came from 8 nations (Belgium, Denmark, France, Germany, Iceland, Italy, Switzerland, and the United Kingdom), and from the European Union. GRIP successfully drilled a 3028 meter ice core to the bed of the Greenland ice sheet at Summit.

GRIP contributes to the aims of the IGBP PAGES program. The GRIP data are held on the WDC-A Paleoclimatology server.

The Program Steering Committee was chaired by:

Dr. B. Stauffer
Physikalisches Institut der Universitat
Bern, Switzerland

The GRIP Steering Committee and Management Group Members Include:

Dr. B. Stauffer
(Steering Committee Chairman)
Physikalisches Institut, Bern, Switzerland
Dr. H. Miller
(Management Group Chairman)
Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany
Dr. H. Clausen
Institute of Geophysics, University of Copenhagen, Denmark
Dr. R. J. Delmas
Laboratoire de Glaciologie & Geophysique de l'Environnement, St. Martin d'HSres, France
Dr. N. Gundestrup
Institute of Geophysics, University of Copenhagen, Denmark
Dr. C. Hammer
Institute of Geophysics, University of Copenhagen, Denmark
Professor S. J. Johnsen
Science Institute of Iceland, Reykjavik, Iceland
Dr. C. Lorius
Laboratoire de Glaciologie & Geophysique de l'Environnement, St. Martin d'HSres, France
Dr. H. Oeschger
PAGES Core Project Office, Bern, Switzerland
Dr. G. Orombelli
Dipartimento di Scienze della Terra, Universitia di Milano, Italy
Dr. D. Peel
British Antarctic Survey, Cambridge, United Kingdom
Dr. R. Souchez
Dept. des Sciences de la Terre & de l'Environnement, Universite‚ Libre Brussels, Belgium
Dr. E. Wolff
British Antarctic Survey, Cambridge, United Kingdom

European Science Foundation

Dr. M. Fratta
Scientific Secretary
Mrs. P. Pirra
Administrative Secretary

Contributing Organizations

Belgium:
Fonds National de la Recherche Scientifique / Nationaal Fonds voor Wetenschappelijk Onderzoek
Denmark:
Statens Naturvidenskabelige Forskningsrtd
France:
Centre National de la Recherche Scientifique (CNRS)
Germany:
Deutsche Forschungsgemeinschaft (DFG)
Iceland:
Rannscknarr Islands
Italy:
Consiglio Nazionale delle Ricerche (CNR)
Switzerland:
Schweizerischer Nationalfonds zur Forderung der wissenschaftlichen
Forschung/Fonds National Suisse de la Recherche Scientifique
United Kingdom:
Natural Environment Research Council (NERC)

Laboratory Address List

This list gives the addresses of the main participating laboratories in GRIP.

Departement des Sciences de la Terre et de l'Environnement
Universite Libre de Bruxelles CP160/03
50 avenue FD Roosevelt
1050 Bruxelles
Belgium

Department of Geophysics
University of Copenhagen
Juliane Maries Vej 30
DK 2100 Copenhagen O
Denmark

Laboratoire de Glaciologie et Geophysique de l'Environnement
BP 96
38402 St. Martin d'Heres Cedex
France

Laboratoire de Modelisation du Climat et de l'Environnement
DSM-CEA, l'Orme des Merisiers
91191 Gif-sur-Yvette Cedex
France

Alfred-Wegener-Institut fur Polar u Meeresforschung
Columbusstrasse
D-2850 Bremerhaven
Germany

Science Institute
University of Iceland
Dunhaga 3
IS-107 Reykjavik
Iceland

Nordic Volcanological Institute
Geoscience Building
University of Iceland
IS-101 Reykjavik
Iceland

Dipart di Scienze della Terra
Via Mangiagalli 34
I-20133 Milano
Italy

Physikalisches Institut
Universitat Bern
Sidlerstrasse 5
CH-3012 Bern
Switzerland

British Antarctic Survey
High Cross
Madingley Road
Cambridge CB3 0ET
United Kingdom

Greenland Ice Core Project Final Report

The "Greenland Ice Core Project, An ESF Research Programme: Final Report" summarizes the results obtained by the GRIP Project. Click to download the report either as a Word 6.0 file (gripfinl.doc) or as an ascii file (gripfinl.txt).