Local summer temperature changes over the past 440 ka revealed by the total air content in the Antarctic EPICA Dome C ice core
(2024) Climate of the Past — Vol. 20, n° 6, p. 1269-1282 (2024)
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- 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 con tent (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.
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Raynaud, D., Yin, Q., Capron, E., Wu, Z., Parrenin, F., Berger, A., & Wu, Z. (2024). Local summer temperature changes over the past 440 ka revealed by the total air content in the Antarctic EPICA Dome C ice core. Climate of the Past, 20(6), 1269-1282. https://doi.org/10.5194/cp-20-1269-2024 (Original work published 2024)