800,000 Deuterium Record and Shorter Records of Various Isotopic Species from Ice Cores

This page provides an introduction and links to ice core records of deuterium (²H) and oxygen-18 (¹⁸O). These are useful indicators of global-scale temperature changes from long before modern instrumental records were begun. This is especially true in Antarctica where ice-cores provide records that extend back almost 800,000 years. Links to isotope data from modern instrumental records can be found at: http://cdiac.ess-dive.lbl.gov/trends/co2/modern_isotopes.html.

The lighter isotopes evaporate preferentially, especially if the water is cold, and the heavier isotopes condense preferentially to become precipitation. Air reaching polar regions is therefore depleted in the heavier isotopes compared to ocean water, and this is especially so during glacial episodes. Thus, ²H and ¹⁸O trapped in annual layers of ice can indicate hemispheric temperature, and, to a lesser extent, global temperature, over several glacial/interglacial cycles. Nitrogen-15 (¹⁵N) can also provide information about diffusion in firn ice, a process which depends on the temperature gradient within the firn; a strong gradient can indicate periods of rapid climate change.

Contributors

Several investigators have contributed to the data set available from the Ice Core Gateway provided by the World Data Center for Paleoclimatology: http://www.ncdc.noaa.gov/paleo/wdc-paleo.html. A complete list is available at: http://www.ncdc.noaa.gov/paleo/icecore.html (Under "obtaining data" click on "list of icecore data").

Some specific projects that have contributed much of the ice-core data are:

• European Project for Ice Coring in Antarctica (EPICA): http://www.esf.org/index.php?id=855
• Greenland Ice Sheet Project (GISP): http://www.gisp2.sr.unh.edu/GISP2-prog_list2.html
• Greenland Ice-Core Project (GRIP): http://www.ncdc.noaa.gov/paleo/icecore/greenland/summit/document/
• CDIAC also has a separate page for the 740,000-year time series of deuterium measurements from the Dome C ice core in Antarctica, available at: http://cdiac.ess-dive.lbl.gov/trends/temp/domec/domec.html

Collective Period of Record

From approximately 800,000 years before "present" (i.e., before 1950) into the 19^th or 20^th Century, depending on the particular core.

Graphics

Antarctic Ice Cores

• Deuterium records (along with carbon dioxide records): http://www.antarctica.ac.uk/press/journalists/resources/science/images/003.jpg
• Slide show with pictures of different phases of ice core projects: http://www.ncdc.noaa.gov/paleo/slides/slideset/15/index.html

Greenland Ice Cores

• Oxygen 18 records (Green) and inferred temperatures from Dome C, Antarctica: http://www.ncdc.noaa.gov/paleo/pubs/jouzel2007/fig2.jpg
• See this journal paper (Figure 1): http://www.lehigh.edu/~ziy2/pubs/Lowe2008QSR.pdf

Data

• Ice Core Isotope Gateway from NOAA paleoclimatology world data center: http://www.ncdc.noaa.gov/paleo/icecore/icecore-varlist.html
• EPICA-specific ice core data: http://www.ncdc.noaa.gov/paleo/icecore/antarctica/domec/domec_epica_data.html
• The 800,000-year deuterium record and temperature reconstruction from Dome C: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc3deuttemp2007.txt
• Vostok-specific ice core data: http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_isotope.html
• Greenland ice-core data: http://www.ncdc.noaa.gov/paleo/icecore/greenland/ngrip/ngrip-data.html
• CDIAC 740,000 ice core deuterium record: http://cdiac.ess-dive.lbl.gov/trends/temp/domec/domec.html

Methods

Extraction of Ice Cores and Dating

A Rotating drill cuts an annulus of ice (typically about 10 cm in diameter) around a core which is extracted in sections of a few meters each. Samples from the core are melted so that gases can readily escape into a vacuum; then the sample is typically refrozen and the process is repeated to extract a larger sample of gases. The time a layer was formed can be found by several means besides counting layers, which has its limitations. The presence of ash from known volcanoes, comparison with ocean sediments, and other means are complimented by a glacial dynamics model, as described by Parrenin (2007).

Measurement

Isotope ratios are then measured by mass spectrometry: http://www.esrl.noaa.gov/gmd/outreach/isotopes/mass_spec.html in which molecules are bombarded with electrons to create ions with particular mass to charge ratios. Accelerated molecules of normal water, H₂O, with 16 atomic mass units (a.m.u.), deuterium (17 a.m.u.) and H₂¹⁸O (18 a.m.u.) will follow different paths when exposed to an electromagnetic field. The number of ions passing along a particular path is measured by an electronic signal.

Reporting Data

The ratio of the amount of a less common stable isotope to that of the most common isotope of that element (isotope ratio) in a sample is compared to the isotope ratio in some standard reference material. The example below provides the general formula, using oxygen-18 as an example.

Value (per mil) = 1000 × [(¹⁸O/¹⁶O)_sample – (¹⁸O/¹⁶O)_reference ]/(¹⁸O/¹⁶O)_reference
= 1000 × {[(¹⁸O/¹⁶O)_sample/(¹⁸O/¹⁶O)_reference] -1}

The multiplier of 1000 is convenient because isotope ratios and their differences are typically small; the results are expressed as per mil. The usual reference material for ¹⁸O and ²H in water is Vienna Mean Standard Ocean Water (V-SMOW) which is a blend of different water samples from around the world. Vostok data are expressed relative to an earlier reference, Standard Mean Ocean Water (SMOW), which was less well defined.

Trends

Isotopic data in ice cores provide information about past temperatures. On the time scales of interest here, Earth's temperature is primarily driven by Milankovitch cycles: http://www.earthobservatory.nasa.gov/Features/Milankovitch/milankovitch_2.php, which result from gravitational influences of other bodies in the Solar System. These influences exert quasi-periodic changes in the shape of Earth's orbit and in the angle between plane of Earth's orbit and the Earth's axis. These changes have resulted in temperature cycles of around 100,000 years each over the last 800,000 years, due to their resonance status over that period of astronomical time. To see a graph of the deuterium record and corresponding CO₂ concentrations at Dome C, Antarctica over the last 800,000 years, see: http://www.antarctica.ac.uk/press/journalists/resources/science/images/003.jpg

References

• F. Parrenin, J.-M. Barnola, J. Beer et al. 2007. The EDC3 chronology for the EPICA Dome C ice core Climate of the Past 3: 485–49 Jouzel, J., V. Masson-Delmotte, O. Cattani et alia. 2007. Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years. Science 317 (5839): 793-797.
• Rasmussen, S.O., I.K. Seierdtad, K.K. Anderson, et al. 2008. Synchronization of the NGRIP, GRIP, and GISP2 ice cores across MIS 2 and palaeoclimatic implications. Quaternary Science Reviews 27: 6–17.
• Sowers, T., Bender, M., and Raynaud, D. 1989. Elemental and isotopic composition of occluded O₂ and N₂ in polar ice, J. Geophys. Res., 94(D4): 5137–5150.
• MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith and J. Elkins. 2006. The Law Dome CO₂, CH₄ and N₂O Ice Core Records Extended to 2000 years BP. Geophysical Research Letters 33, 14, L14810 10.1029/2006GL026152.

Citing the Ice-Core Data

General instructions for citing data from the World Data Center for Paleoclimatology can be found at: http://www.ncdc.noaa.gov/paleo/citation.html.

If citing material from this page only, cite as: 800,000 Year Ice-Core Records of Isotopes ²H, ¹⁸O, and other isotopic species, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy. Path: http://cdiac.ess-dive.lbl.gov/trends/co2/ice_core_isotopes.html.