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This programme has been motivated primarily by the urgent need to predict more accurately how global climate is likely to respond to increased emissions of greenhouse gases as a result of human activities. In order to predict the future, it is necessary to determine how global climate has responded to variations in greenhouse gas concentrations in the past, in combination with other forcing factors such as changes in solar output and in the earth’s orbit.
The polar ice sheets are the only archive preserving information about changes both in past climate and in the atmosphere’s composition. Valuable information covering at least a full climatic cycle (the last 150,000 years) has already been obtained from deep ice cores drilled through the Greenland and Antarctic ice caps. However, the Antarctic ice sheet spans an area comparable to the size of Europe and it covers a correspondingly wide range of both climatological and glaciological regimes. No single site can deliver a climate record that is representative of the whole continent, nor yield a record that has optimal resolution across the whole time range of interest. New high resolution records from Antarctica are needed to complement the records recently obtained in central Greenland. There is also a need to go back further in time to ascertain whether recent patterns are relatively unique, or typical of other climatic cycles.
EPICA has been developed in collaboration with the European Commission to meet these objectives. Fresh technical challenges have had to be overcome, mainly due to the much lower temperatures in continental Antarctica compared with Greenland, and the necessity to work in unexplored regions, requiring extensive meteorological and geophysical work to select drill sites. A new drill has been designed, built and tested in North Greenland, drawing on the designs of drills used successfully in the Greenland Ice Core Project (GRIP) and by Japan in central East Antarctica.
The ESF EPICA Programme has provided support for the EPICA Scientific Steering Committee to co-ordinate the drilling activities of EPICA, which have been supported by the European Commission, the logistic partners in Antarctica (IPEV/PNRA for Concordia Station; AWI for Kohnen Station) and national operators.
In the framework of the EPICA Programme, annual scientific workshops have been organised, as well as smaller, more focussed meetings for the drilling team.
The ESF EPICA Programme has also regularly supported core processing by an international team of scientists at AWI Bremerhaven.
Scientific papers resulting from the EPICA work can be found on the website of the Institute for Marine and Atmospheric Research Utrecht (IMAU) Go to Website
Introduction
The single most important source of information about past climate change and the associated composition of the atmosphere are the two large ice caps of Greenland and Antarctica. Analysis of ice cores is therefore the most powerful means we have to determine how climate has changed over the last few climate cycles, and to relate this to changes in atmospheric composition, in particular to concentrations of the principal greenhouse gases - CO2, CH4 and N2O (carbon dioxide, methane, and nitrous oxide).
Recent deep-drilling efforts have focused more on central Greenland, notably the highly successful ESF Greenland Ice Core Project (GRIP) and the US Greenland Ice Sheet Project (GISP2) at Summit. Studies of the vast East Antarctic plateau have so far been limited to a single core obtained at Vostok and to a recent drilling by the Japanese at Dome Fuji, neither of which have reached bedrock. EPICA is designed to complement the Greenland projects, and determine whether some of the results obtained from these earlier studies have global significance or are confined chiefly to the Arctic region. It also aims to achieve one of the longest possible climate records from Antarctica, at a site where the record is likely to require minimal correction for ice flow, by drilling to bedrock at an ice dome.
Records from Vostok, Antarctica, have shown a close correlation between climate and greenhouse gas concentrations that now extends to 240 ka. The central Greenland cores obtained by GRIP, and also by GISP 2 (Greenland Ice Sheet Project) have confirmed the existence of rapid and large oscillations during the last glacial period and the end of the last transition (between ice age and current warmer period). One interesting question that EPICA can help determine is whether these oscillations were a global phenomenon, or confined to a large part of the Northern Hemisphere where geographical conditions might favour them.
Other important questions that EPICA should help answer include whether the climatic stability of the last 10,000 years, which contrasts with extreme climate variability through most of the rest of the last glacial, is an exception for the last 500,000 years, and how global climate changes are coupled between the two hemispheres.
The EPICA programme
EPICA is an ambitious programme to drill deep cores in two different regions of Antarctica. The aim is to achieve optimal resolution at different time scales, and to obtain a broader perspective relating to the Antarctic continent as a whole. However, to ensure that logistic operations and also the ice core analysis capabilities of European laboratories are not overloaded, the two sites will be drilled consecutively, splitting the programme into two halves.
The first phase, lasting five years, focussed on the longer time period spanning the last few glacial to interglacial cycles going back ~500,000 years. To do this, a 3,300 metre long core is being drilled at Dome C south of the Indian Ocean in East Antarctica. The exact drilling site was selected with a geodetic and geophysical survey in the austral season 1995-96 to single out the thickest and least disturbed ice sequence, in order to obtain a long and continuous climate record. This is also an excellent location for setting the whole Antarctic record into a global context, in particular enabling comparisons with the Greenland record in the north, and with long continental and ocean records from all over the globe.
While this first phase of drilling was taking place, a detailed geophysical and geochemical reconnaissance was made in Dronning Maud Land, to identify optimal sites for deep drilling. This region of Antarctica is most strongly influenced by the Atlantic ocean, and was chosen because the cores obtained here, in a region of higher snow accumulation rate, will provide finer grained detail on the last glacial cycle.
A particular goal is to investigate in detail the climatic changes in Antarctica during the sequence of rapid climate oscillations recorded in the GRIP core from Greenland during the last glacial, and to study evidence for time-phase differences between events recorded in the two hemispheres. The Dome C core will have inadequate resolution to resolve this issue for the last glacial cycle, although significantly it will help establish whether similar events occurred in earlier glacial cycles.
This is one of the biggest tests yet of the ability of European laboratories to cooperate in a large complex project. However, the ice-core laboratories involved have already learnt to integrate their research efforts within GRIP, and this is an opportunity for them to consolidate this as a basis for an emerging European network for Antarctic and Arctic activities.
Scientific background
There is widespread concern that emissions of carbon dioxide and other greenhouse gases will cause a significant rise in global air temperatures by the middle of the next century. But although there is little doubt that there is a close relationship between atmospheric greenhouse gas levels and global temperature, there is still great uncertainty over the likely extent and speed of the changes, and how they will be distributed regionally.
There are two principal findings from earlier ice core studies in central Greenland and Vostok, Antarctica, that need further confirmation and extrapolation back in time. The first is the expected close correlation between climate and greenhouse gas concentrations extending back to 240 ka, as indicated by the ice core record from Vostok.
On the other hand, the second finding from central Greenland ice cores was much less expected, confirming a series of large and rapid oscillations in climate during the late part of the last glacial period and during the transition, which occurred within the time span of a human lifetime. Then, just as unexpected, was the revelation from the GRIP isotopic and chemical record that similar oscillations may have occurred during the last interglacial 110 -140 ka ago. However, although the GRIP and GISP2 records match almost exactly back to 110,000 years ago, below this depth significant structural disturbances are observed in both cores, and the records start to diverge. Most probably, one or both records has been affected by flow disturbances in the lowest part of the ice sheet.
Ice drill programmes have the twin goals of identifying changes in past climate and in atmospheric chemistry. One of the principal ways of identifying climate change is to determine the proportions of the stable oxygen 18 and deuterium (hydrogen 2) isotopes at different levels of the core through their presence in water. As HDO and H218O are heavier molecules than standard H216O, they have a slightly lower saturation vapour pressure than the lighter ones, and the proportions observed in precipitation change as an air mass becomes depleted as it moves polewards from source regions over the oceans. As a result, there is an approximately linear relationship between the mean isotopic content of snow and the mean annual temperature, although additional influences relating to conditions in the source region of the air masses providing the Antarctic precipitation need to be considered.
Equally important is to reconstruct the record of past atmospheric chemistry, including aerosols and water soluble gases, in addition to the composition of atmospheric gases trapped in bubbles within the ice. A variety of techniques is used here, including continuous flow analysis to measure H2O2, NH4, and HCHO. Sodium, calcium and sulfate levels are also measured, as these provide information, respectively, on past atmospheric concentrations of sea salt (Na), soil dust (Ca), and secondary aerosols derived from sulphur, including marine biogenic and volcanic emissions.
All these measurements would be of little value, however, without accurate dating of the ice cores. For the last 50 ka this is relatively straightforward, as detailed information has already been obtained from Central Greenland cores (GRIP and GISP2) and from a core obtained in the western Antarctic deep Byrd ice. Dating of the new cores can then be performed by matching acidic sulphur signals against volcanic horizons identified within the Byrd core. To extend the dating back to 250,000 years other techniques are needed, and include ice-flow modelling controlled by matching features in the new cores (eg. changes in atmospheric gas isotopic and chemical composition) with corresponding features in the ice cores from Vostok and central Greenland as well as with the ocean sediment records.
In this regard, developments in the ESF’s European Ice Sheet Modelling Initiative are expected to provide improved methods for dating the cores and separating climatic signals from ice-sheet signals (i.e. changes in topography/ice flow).
Aims and objectives
EPICA’s two broad objectives were firstly to obtain a full documentation of the Antarctic climate record and then to compare this as optimally as possible with the Greenland record. To do this two more cores were needed to cover the extremes of time scale, with one at a site of higher annual snowfall to provide a detailed record of events over the last glacial cycle, and the other in a region of low snow accumulation to allow changes over several glacial cycles to be recorded at a lower resolution. Furthermore, the complex structure of the atmosphere over Antarctica, and its interactions with the surrounding ocean, make it necessary for ice cores from several locations to be analysed (i.e. the two EPICA cores plus the earlier ones) in order to achieve a continental perspective. Taken together the two cores are expected to shed light on the following key questions not answered by the results from either the Greenland cores, or the earlier Vostok drilling in Antarctica.
- Are the rapid climatic changes of the last ice age cycle global events, or are they restricted largely to part of the Northern Hemisphere, where it is possible that geographic conditions favour them?
- Are these rapid changes unique to the last glacial cycle or did they occur in previous cycles as well?
- Is the relatively warm stable climatic period of the last 10,000 years an exception for the last 500,000 years?
- Do the transitions from the glacial to warm periods and back again always follow the same pattern or is a variety of mechanisms involved?
- Are global climate changes always triggered in the northern Hemisphere or is the opposite sequence possible?
- How are global climate changes coupled between the two hemispheres?
The answers to all these questions have an important bearing on the ability to predict future climate, and in particular to assess the impact of anthropogenic effects. The archives obtained from the cores will also provide unique evidence on the role of the different elements in the climate equation, including forcing factors (greenhouse gases etc), climate variability, and long term climate/ice sheet interactions. In addition, the ice cores will tell us more about the history of the ice sheet itself, which is very relevant to our understanding of sea-level rises.
The ultimate prize is to obtain as full an understanding as possible of the mechanisms driving both global climate change and the coupled biogeochemical cycles, to give the required perspective for assessing current and imminent changes. To reach this understanding it is necessary to study past changes over several different time scales, which EPICA is therefore doing. The Atlantic sector site will encompass the last climatic cycle in detail to examine processes responsible for short term fluctuations of the type observed from the Greenland cores. The snow accumulation rate there is sufficiently high for changes to be resolved at least down to the scale of individual seasons. By contrast, the Dome C site will cover at least five glacial cycles, with the aim here being to compare the processes of major climate change in each case. However, the resolution should still be high enough to ascertain whether the rapid oscillations observed at times of climate change during the last cycle also occurred in earlier cycles.
Basic data on the two EPICA drilling sites
Concordia Station, Dome C | Kohnen Station, Dronning Maud Land | |
Co-ordinates | 75°06’04"S; 123°20’52"E | 75°00'06"S; 00°04'04"E |
Altitude (above sea level) | 3233 m | 2892 m |
Mean annual surface temperature | -54.5°C | -44.6°C |
Mean annual accumulation rate | 25.0 kg m-2 year-1 | 64.0+0.5 kg.m-2.year-1 |
Measured ice thickness | 3309±22 m | 2750+50 m |
Notation of ice cores | EDC96 and EDC99 |
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EPICA completes drilling at Dome C
On Tuesday 21 December 2004, a European team involved in EPICA reached the drilling depth of 3270.2 m, which is 5m above the bedrock at Dome C, on the central plateau of the east Antarctic ice sheet. The ice is melting at the bedrock and it has been decided to stop at this depth to avoid any danger of direct contamination of the basal water. The drilling operation has therefore been terminated.
The drilling has been very successful and has been followed by a wide community of ice and climate researchers. The 70 meters of ice drilled this season completes a long venture started in 1996. The core has already led to the release in the scientific journal « Nature » last June of a 740,000-year record of Antarctic climate. The new piece of core will extend the record to an age estimated to be more than 900.000 years old. This is the oldest ice that has been recovered from deep ice cores. The basal ice has ice crystals, some bigger than 40 cm and we have observed many inclusions of brown/reddish material mainly between the big ice crystals.
The prospect of the new and unknown information to be found by studies of the ice from the EPICA DomeC ice core is fascinating and may have a profound impact on our understanding of the Earth’s climate and environment.
EPICA completes drilling at Kohnen Station
EPICA deep drilling at Kohnen station, Dronning Maud Land, was terminated on 17 January 2006 at a logged drilling depth of 2774.15 m.
EPICA Publications
On behalf of the EPICA Steering Comittee, the Institute for Marine and Atmospheric research Utrecht (IMAU) maintains a database and a listing of accepted EPICA publications. These publications have been assigned an EPICA publication number and include a formal EPICA acknowledgements paragraph.
Go to Website
EPICA Community paper
The EPICA community published its second article in Nature on 9 November 2006 - 'One-to-one coupling of glacial climate variability in Greenland and Antarctica' (Vol. 444, pp 195-198).
An earlier article written by the EPICA community was published by the scientific journal Nature on 10 June 2004. A pdf file of the article, ’Eight Glacial Cycles from an Antarctic Ice Core’, may be downloaded here (PDF 380 KB).
For further information about Nature and its contents Go to Website
EPICA publishes atmospheric records in Science
COVER Drill head with piece of an ice core retrieved on 30 November 2002 at Dome Concordia Station during the European Project for Ice Coring in Antarctica. This ice is from a depth of 2873 meters and is about 491,000 years old. The ice core contains a continuous record of greenhouse gases over the past 650,000 years. Science 25 November 2005: | Atmospheric Methane and Nitrous Oxide of the Late Pleistocene from Antartic Ice Cores Renato Spahni1, Jérôme Chappellaz2, Thomas F. Stocker1*, Laetitia Loulergue2, Gregor Hausammann1, Kenji Kawamura1**, Jacqueline Flückiger1***, Jakob Schwander1, Dominique Raynaud2, Valérie Masson-Delmotte3, Jean Jouzel3 The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 ± 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 ± 7 ppbv, slightly higher than early Holocene values.1 Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. 2 Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE, CNRS-UJF), CNRS, 54 Rue Molières, 38402 St. Martin d’Hères, Grenoble, France. 3 Institut Pierre Simon Laplace/Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS 1572, CE Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France. ** Present address: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0244, USA. *** Present address: Institute of Arctic and Alpine Research, University of Colorado at Boulder, 450 UCB Boulder, Colorado 80309–0450, USA. |
* To whom correspondence should be addressed:
- ThomasStockerE-Mail
- University of BernFaculty of SciencePhysics InstituteDepartment of Climate & Environmental PhysicsBernSwitzerland
