Concentration and Isotopic Composition of O₂ and N₂ in Trapped Gases of the Vostok Ice Core

Data Set Summary

These data describe the ¹⁸O of O₂, ¹⁵N of N₂, ¹⁸O_atm, and O₂/N₂ ratios of trapped gases in the Vostok ice core from East Antarctica. The investigator used a mass spectrometer to measure gas concentrations and isotopic compositions. Data extend to approximately 420,000 years ago. Two different age models are included.

Data are available in tab-delimited ASCII format via ftp.

Citing These Data:

Please cite these data as follows:

Bender, M. 2002. Vostok ice core trapped gas concentrations and isotopic compositions. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5862DCW.

Overview Table

Category	Description
parameter(s)	oxygen and nitrogen isotopes in trapped gases
spatial coverage	ice core obtained at Vostok Station, East Antarctica
temporal coverage	data extend to approx. 420,000 years ago
data format	tab-delimited ASCII
file size	files sizes range from 9 KB to 132 KB
procedures for obtaining data	data are available via ftp

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments:

Investigator Name and Affiliation:

Dr. Michael Bender
Department of Geosciences
Princeton University
Princeton, NJ     USA

Technical Contact:

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgments:

Todd Sowers, Joseph Orchardo, Bruno Malaize, and Mary-Lynn Dickson helped with sample analysis.

2. Detailed Data Description:

Format:

Data consist of four tab-delimited ASCII files. For a description of these files, see Sample Data Records.

File Size:

File sizes range from 9 KB to 132 KB.

Sample Data Records:

"Vos_O2-N2_isotope_data_all" contains all data for the 4G, 3G, and 5G cores:

Core  Depth     del 15N     del 18O  del 18Oatm   del O2/N2
					
5G    174.5     0.49	     1.09      0.11         -28.2
5G    174.5     0.56	     1.14      0.01         -35.2
5G    185.2     0.58	     0.97     -0.19         -26.4
5G    185.2     0.58	     0.99     -0.18         -30.5

"Vos_O2-N2_isotope_data_avg" contains average values of the properties at given depths:

Core  Depth     del 15N     del 18O  del 18Oatm   del O2/N2
					
5G    174.5     0.53         1.11      0.06         -31.7
5G    185.2     0.58         0.98     -0.19         -28.4
5G    205.7     0.56         0.94     -0.18         -34.0

"Vostok_EGT20_chronology" contains gas ages and ice ages assigned to each depth according to the EGT20 chronology (see Temporal Coverage). Gas age-ice age differences are included under the header "EGT20 *age."

Depth   EGT20 ice age   EGT20 *age   EGT20 gas age
			
150     5.721           3.319        2.402
151     5.769           3.307        2.462
152     5.816           3.306        2.51
153     5.863           3.315        2.548

"Vostok_d18Oatm_chronology" contains gas ages and ice ages assigned to each depth according to the ¹⁸O_atm chronology (see Temporal Coverage). Gas age-ice age differences are included under the header "EGT20 *age."

Depth   18Oatm ice age   EGT20 *age   18Oatm gas age
			
150     5.68             3.32         2.36
151     5.72             3.31         2.42
152     5.77             3.31         2.47
153     5.82             3.32         2.50

Spatial Coverage:

Sampled ice cores came from Russia's Vostok Station in East Antarctica, located at 72.28 degrees south latitude, 106.48 degrees east longitude.

Study Area Location Map:

Vostok Station is indicated on the map below by the letter "V." Crosshairs mark the position of the south pole.

Temporal Coverage:

Data extend to 3623 meters depth, or approximately 420,000 years ago (i.e., 420 ka).

Isotopic data are presented along with two proposed chronologies. The first is the Extended Glaciological Timescale (EGT20), a minimally tuned glaciological chronology utilized by Petit et al. (1999). The second is an orbitally tuned chronology that exploits the strong relationship between ¹⁸O_atm and insolation changes. This chronology, described by Petit et al. (1999), is enhanced by control points that assume correspondence between insolation maxima and the midpoints of decreases in ¹⁸O_atm. An additional control point at 385 ka gas age has been added here. The ¹⁸O_atm chronology utilizes gas age-ice age differences from the EGT20 timescale.

Parameter or Variable:

Data describe the ¹⁸O of O₂, ¹⁵N of N₂, ¹⁸O_atm, and O₂/N₂ ratios of trapped gas samples from the Vostok ice cores. All results are reported with respect to the standard of late twentieth-century air.

3. Data Access:

Data are available via ftp.

Related Data Collections:

• Reusch: Central West Antarctic Glaciochemistry from Ice Cores
• Severinghaus, Grachev, and Battle: Firn Air Isotope and Temperature Measurements from Siple Dome and South Pole
• Albert: Snow and Firn Temperature and Permeability Measurements from Siple Dome, Antarctica

4. Data Acquisition and Processing:

Theory of Measurements:

¹⁸O_atm is a useful variable for correlating ice cores, and for inferring information about past climate and ice extent. At any given time, ¹⁸O is approximately constant throughout the atmosphere, but this value varies over time due to changes in the hydrologic cycle, ice sheet volume, and worldwide patterns of plant growth. The ¹⁸O of O₂ in the past atmosphere (¹⁸O_atm) is calculated by subtracting 2x¹⁵N from ¹⁸O, thus correcting for gravitational fractionation, a process that occurs while air is trapped within the firn prior to being isolated from the atmosphere.

Another effect results from how gases are retained within an ice core. The ratio of O₂ to N₂ trapped within the core is typically less than the original ratio of the trapped air because O₂ is a smaller molecule than N₂, and thus escapes more readily from the core as bubbles form and during core storage. ¹⁵N of N₂ has a constant value of zero in the atmosphere, but is greater than zero in firn air due to gravitational fractionation. ¹⁸O of O₂ is also enriched by gravitational fractionation.

Data Acquisition Methods:

The investigator collected trapped gases by melting ice samples in a vacuum, refreezing them, and condensing the headspace gases into a stainless steel tube immersed in liquid helium. Trapped gases were admitted to the mass spectrometer and analyzed versus a dry air standard to determine the isotopic composition of N₂, the isotopic composition of O₂, and the O₂/N₂ ratio. Methodology followed that of Sowers et al. (1989), except that the investigator did not remelt and refreeze samples after the initial collection. This change in methodology caused loss of O₂, which is more soluble than N₂, and thus lowered the measured O₂/N₂ ratios slightly.

5. References and Related Publications:

Petit, J. R., J. Jouzel, D. Raynaud, N. I. Barkov, J.M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, V. M. Kotlyakov, M. Legrand, V. Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman, and M. Stievenard. 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.

Sowers, T., M. Bender, and D. Raynaud. 1989. Elemental and isotopic composition of occluded O₂ and N₂ in polar ice. Journal of Geophysical Research 94: 5137-5150.

6. Document Information:

Document Creation Date:

30 January 2002

Document Revision Date:

14 February 2002

Document Curator:

NSIDC writers

Document URL:

http://nsidc.org/data/docs/agdc/nsidc0107_bender/index.html