High-resolution carbon dioxide concentration record 650,000-800,000 years before present

Area of Science:

• Paleoclimatology
• Ice Core Science
• Atmospheric Chemistry

Background:

• Atmospheric carbon dioxide (CO2) levels are critical for understanding Earth's climate.
• Antarctic ice cores provide valuable records of past atmospheric composition.
• Previous records from Vostok and EPICA Dome C extended to 650,000 years.

Purpose of the Study:

• To extend the atmospheric CO2 record further into the past.
• To investigate CO2 concentrations during past glacial cycles.
• To analyze the relationship between CO2 and Antarctic temperature over longer timescales.

Main Methods:

• Analysis of air trapped in the lowest 200 m of the EPICA Dome C ice core.
• Measurement of carbon dioxide concentrations using gas chromatography.
• Comparison of CO2 data with Antarctic temperature reconstructions.

Main Results:

• The atmospheric CO2 record was extended to 800,000 years before present, covering two additional glacial cycles.
• Atmospheric CO2 concentrations are strongly correlated with Antarctic temperature across eight glacial cycles.
• Significantly lower CO2 concentrations (below 180 p.p.m.v.) were observed between 650,000 and 750,000 years ago, including a 3,000-year period below 180 p.p.m.v. during Marine Isotope Stage 16.
• The lowest CO2 concentration measured was 172 parts per million by volume (p.p.m.v.), extending the pre-industrial range.

Conclusions:

• Past atmospheric CO2 levels exhibit a strong correlation with Antarctic temperature over multiple glacial-interglacial cycles.
• The extended ice core record reveals periods of exceptionally low CO2 concentrations, potentially linked to enhanced oceanic carbon storage.
• This research refines our understanding of the natural variability of atmospheric CO2 and its relationship with climate over the past 800,000 years.