Past Antarctic summer temperature revealed by total air content in ice cores

• Main Authors: Raynaud, Dominique, Yin, Qiuzhen, Capron, Emilie, Wu, Zhipeng, Parrenin, Frédéric, Berger, André, Lipenkov, Vladimir
• Format: Text
• Language: English
• Published: 2024
• Subjects: Antarctic; Tac; The Antarctic; Antarc*; EPICA; ice core; Ice Sheet
• Online Access: https://doi.org/10.5194/egusphere-2023-2360; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2360/

Seasonal temperature reconstructions from ice cores are missing over glacial–interglacial timescales, preventing a good understanding of the driving factors of Antarctic past climate changes. Here the total air content (TAC) record from the Antarctic EPICA Dome C (EDC) ice core is analyzed over the last 440 ka (thousand years). While the water isotopic record, a tracer for annual mean surface temperature, exhibits a dominant ∼100 kyr cyclicity, the TAC record is associated with a dominant ∼40 kyr cyclicity. Our results show that the TAC record is anti-correlated with the mean insolation over the local astronomical summer half-year. They also show for the first time that it is highly anti-correlated with local summer temperature simulated with an Earth system model of intermediate complexity. We propose that (1) the local summer insolation controls the local summer temperature; (2) the latter, through the development of temperature gradients at the near-surface of the ice sheet ( <2 m), is affecting the surface snow structure; and (3) those snow structure changes propagating down to the bottom of the firn through densification are eventually controlling the pore volume at the bubble close-off and consequently the TAC. Hence, our results suggest that the EDC TAC record could be used as a proxy for local summer temperature changes. Also, our new simulations show that the mean insolation over the local astronomical summer half-year is the primary driver of Antarctic summer surface temperature variations, while changes in atmospheric greenhouse gas (GHG) concentrations and Northern Hemisphere (NH) ice sheet configurations play a more important role in Antarctic annual surface temperature changes.