Temperature and atmospheric CO2 from Dome C for 800 000 years

Antarctic ice cores reveals close temperature and carbon dioxide correlation for eight glacial-interglacial cycles

A recent study of ice cores from Antarctica provides a climate record for the past 800,000 years.  The ice cores were drilled 3,139 m deep at the Dome C station in eastern Antarctica. From the ice cores it is possible to determine CO2, CH4 and dust concentrations and proxies for air temperature.  The analysis reveals that atmospheric carbon dioxide was strongly correlated with Antarctic temperature throughout eight glacial cycles.

Introduction

The European Project for Ice Coring in Antarctica (EPICA) is a consortium of laboratories and Antarctic logistics operators from ten nations. Its goal is to recover two deep ice cores in East Antarctica. The study of one core (EDML) from Kohnen Station in the Dronning Maud Land sector of Antarctica is aimed at producing a high-resolution record of at least one glacial–interglacial cycle in the sector of Antarctica facing the Atlantic Ocean, for comparison with Greenland records. The second core (EDC) from Dome C, discussed here, is aimed at producing a record of the longest time period possible.

Observations

Observations over 800,000 years from EPICA ice cores
EPICA Dome C ice core record
(a) Calculated insolation. Upper blue curve (left axis), mid-July insolation at 65° N; lower black curve (right axis), annual mean insolation at 75°S (the latitude of Dome C).
(b) Dome-C delta-D (3,000-yr averages). Vostok delta-D (red) is shown for comparison. Some MIS stage numbers are indicated.
(c) Marine delta-18O record from different sites
(d) Dust from EPICA Dome C.

The Dome C site has an ice thickness of 3,309 meters. The first core was recovered with a drilling depth of 3,190 m, of which 3,139 m had been analyzed at the time of this paper for several constituents including deuterium excess, delta-oxygen-18, and atmospheric CO2 and CH4. This ice core provides a climate record for the past 740,000 years.

For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by lower temperatures in interglacial periods in Antarctica, but the interglacial was a greater proportion of each glacial/interglacial cycle.

Temperature and atmospheric CO2 from Dome C for 800 000 years
Comparison of temperature and CO2
Temperature from Dome C with respect to the mean temperature of the last millennium (black curve)
CO2 from Dome C (solid circles in purple, blue, black; red open circles), Taylor Dome (brown) and Vostok (green).
Horizontal lines are mean values of temperature and CO2 for the time periods 799–650, 650–450, 450–270 and 270–50 thousand years ago.
Glacial terminations are indicated by Roman numerals in subscript; Marine Isotope Stages (MIS) are given in italic Arabic numerals. Source Lüthi et al. 2007

Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Results of the lowest 200 meters of the Dome C ice core extend the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 years before present. The analysis reveals that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles. Between 650,000 and 750,000 yr before present CO2 concentrations were significantly lower than in the more recent cycle

Sources:

Eight glacial cycles from an Antarctic ice core, EPICA community members, Nature 429, 623-628 (10 June 2004)

High-resolution carbon dioxide concentration record 650,000–800,000 years before present, Dieter Lüthi, Martine Le Floch, Bernhard Bereiter, Thomas Blunier, Jean-Marc Barnola, Urs Siegenthaler, Dominique Raynaud, Jean Jouzel, Hubertus Fischer, Kenji Kawamura & Thomas F. Stocker, Nature 453, 379-382 (15 May 2008) doi:10.1038/nature06949