Ice Coring: A Special Selection

24 May 2005 - Articles, Logistics, Ice & Snow

More than three kilometres worth of ice cores

The Greenland icecap is the principal site in the Northern Hemisphere for ice-coring campaigns. Since 1989, European researchers have been working at the summit of the ice sheet where it is the thickest and most stable with respect to its flow towards the coast. Several countries have also set up ice drilling stations in the Antarctic: the United States, Russia, Japan, etc. However, it is the Europeans who have brought to the surface the most ancient ice cores ever extracted from the ice sheet.

In the Arctic

The first international extraction site was set up in 1989, and over several drilling seasons, the European project, GRIP (GReenland Ice core Project) made it possible to extract cores reaching right down into the bottom layers of the ice cap at 3,027 metres deep.

At the same time, a second drilling site, American this time, was started 28 kilometres to the west of the Summit station used by the GRIP.

The American project, baptised GISP2 (Greenland Ice Sheet project Two) also collected a long ice core, which reached 3,053 metres down to the bottom of the ice cap and 1.55 metres beneath it into the rocky substrate on which it sits.

However, the quality of the deepest, and thus the most ancient samples, was not as good as had been hoped for by researchers. The GRIP and GISP2 drilling operations were reliable enough to enable climate studies going back as far as 105,000 years, but the ice samples collected from periods before that were of less scientific interest.

Thus, following on from these campaigns, a new European campaign, coordinated by Denmark and bringing together teams from the USA and Japan, was set up and named the NGRIP (North GReenland Ice core Project). The drilling site, 300 kilometres further north than the GRIP and GISP2 stations, started in 1996, and rock was reached in July 2003. The station was closed in the summer of 2004.

The early scientific results of this latest campaign have just been published by the researchers . Apart from being the deepest ice core ever collected in Greenland, the data covers approximately 125,000 years and reveals that before the last Ice Age, which started 115,000 years ago, the Greenland climate was hot (interglacial period) and stable, without any abrupt variations, thus confirming that the fluctuations observed for this period in the GRIP core arose from the ice having thawed rather than from the climatic changes themselves.

For further information:

In the Antarctic

Several countries have set up ice drilling stations in the Antarctic: the United States, Russia, Japan, etc. However, it is the Europeans who have brought to the surface the most ancient ice cores ever extracted from the ice sheet, in the context of its ambitious project called EPICA (European Project for Ice Coring in Antarctica).

Set up in 1995, the EPICA project comprises two drilling sites in the eastern Antarctic. The Concordia station (or Dome C) is situated at 123° East, 75°06' South, while the Kohnen station, in the territories of Dronning Maude Land, is sited at 00°04' East and 75°00' South. Epica is a research project common to the European Commission and the European Science Foundation, and involves scientific teams from some ten countries.

The ambitious aim of this programme was to go back as far as possible in the climatic history of our planet. In 2004, after eight years of efforts, this target was achieved. With more than 3 kilometres of ice cores extracted at Dome C, researchers now have samples available to them which are some 900,000 years old. This is the most ancient climatic reconstitution ever achieved from ice cores, being twice as old as the findings of the Vostok drilling station (400,000 years in 1999) and Dome Fuji (350,000 years in 2003).

Most recent results

The most recent results of EPICA were published in Nature on June 10, 2004, and the cover of the journal was devoted to this event. The authors highlighted three major findings :

" "Over the past 740,000 years, Earth has experienced 8 climate cycles, alternating between glacial periods and warmer, so-called interglacial periods, with an abrupt change in the rhythm of these cycles which occurred 420,000 years ago. Thus warmer periods during the last 420,000 years were characterised by temperatures similar to those we have today, while previous interglacial periods were colder but lasted for longer. This contrasts with what scientists previously thought was the case.

" The longest warm period during the past 740,000 years took place 420,000 years ago and lasted for about 28,000 years. This period could be considered as "analogous" with that which we are currently experiencing, particularly since the astronomic conditions, the orbit and axis of Earth which influence exposure to the sun, are identical. These results suggest that the next entry into a glacial period will not happen for several thousand years, but the conclusions of detailed analyses are not yet available.

" An analysis of the air bubbles trapped in the ice confirms that the current levels of greenhouse gases are the highest ever reached during the past 440,000 years".

For further information:

EPICA Project Members, Eight glacial cycles from an Antarctic ice core. Nature, 429, 623-628, 2004.
European Project for Ice Coring in Antarctica (EPICA) on the AWI's website
European Project for Ice Coring in Antarctica (EPICA) on the European Science Foundation's website
European Project for Ice Coring in Antarctica (EPICA), a press release by the British Antarctic Survey (BAS)

North-South comparisons reveal the functioning of the world climate machine

Comparison of ice sample drilling results from the Northern Hemisphere with those from the Southern Hemisphere suggest that for the same years, local "climates" were not always identical, with phase shifts of thousands of years.

These intervals between a climatic event in the north and the corresponding reaction recorded in southern ice can be explained by planetary mechanisms for climatic communication, in particular, the reaction time of major ocean currents. This phenomenon is now well understood with respect to links between the Atlantic and Antarctic Oceans. However, future drilling campaigns should help determine more clearly the role played in this vast heat exchange mechanism by the Pacific Ocean, the other great ocean linking the planet's two hemispheres.

By: Gauthier Chapelle