[A-CC33] Ice cores and paleoenvironmental modeling

[ACC33-P01] Surface temperature reconstruction from the penultimate glacial maximum to the last interglacial in inland Antarctica

*Ikumi Oyabu¹, Kenji Kawamura^1,2, Christo Buizert³, Frédéric Parrenin⁴, Ryu Uemura⁵, Motohiro Hirabayashi¹, Kumiko Goto-Azuma¹, Jun Ogata¹, Kyotaro Kitamura¹, Kaori Fukuda¹, Shuji Fujita^1,2 (1.National Institute of Polar Research, Research Organization of Information and Systems, 2.SOKENDAI, 3.Oregon State University, 4.Institut des Géosciences de l’Environnement, 5.Nagoya University)

Keywords:Antarctica, Dome Fuji, Surface temperature, last interglacial

The last interglacial period (LIG, Marine Isotope Stage 5e) attracts much attention as a potential future analogue for an anthropogenically warming world. According to various paleoclimatic reconstructions, the LIG was warmer than the pre-industrial late Holocene, and the global sea level was higher than today by about 5 to 9 m (contributions from both Greenland and Antarctic ice sheets). However, the LIG temperatures on the polar ice sheets are not well constrained. The LIG surface temperatures on the East Antarctic plateau estimated from oxygen and hydrogen isotopic ratios in ice cores are ~4 K higher than pre-industrial, which are broadly consistent with modern spatial relationship between the surface temperature and isotopic ratio (e.g., Jouzel et al., 2007; Uemura et al., 2018). However, determining the temperature-isotope relationship is indeed complex, thus independent surface temperature estimates are highly desired (Buizert et al., 2021).
In this study, we used published δ¹⁵N data (Oyabu et al., 2022) and new CH₄ concentration and stable water isotope ratios from the Dome Fuji (DF) ice core from the penultimate glacial maximum (PGM) (~140 ka BP) to the LIG (~127 ka BP), and inverted them with a firn densification-heat transport model to reconstruct the surface temperature and accumulation rate (Buizert et al., 2021). The CH₄concentration and stable water isotope ratios were measured using a Continuous Flow Analysis (CFA) system at NIPR. The inversion method with the firn densification model requires an ice age scale, Δage, and δ¹⁵N. The ice age scale was constructed by a previous study (Oyabu et al., 2022) with various types of age markers including the new δO₂/N₂ tie points. Δages from the PGM to the LIG were estimated by assuming bipolar seesaw between the peak of δ¹⁸O and abrupt CH₄ increase, and by converting the depth difference between gas and ice depths (Δdepth) to Δage using the ice age scale. Our result shows that the peak LIG surface temperature at DF was ~2 K higher than preindustrial, which is slightly lower than the estimates from water isotopes (e.g., Uemura et al., 2018) but consistent within the range of uncertainty.

References
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Uemura, R., et al., 2018. Asynchrony between Antarctic temperature and CO2 associated with obliquity over the past 720,000 years. Nature Communications 9, 793–11.
Buizert, C., et al., 2021. Antarctic surface temperature and elevation during the Last Glacial Maximum. Science 372, 1097–1101.
Oyabu, I., et al., 2022. The Dome Fuji ice core DF2021 chronology (0-207 kyr BP). Quaternary Science Reviews 294, 107754.