[A-CC29] アイスコアと古環境モデリング

[ACC29-P01] Effects of LGM sea surface temperature and sea ice extent on the isotope-temperature slope at polar ice core sites

*Alexandre CAUQUOIN^1,2、Ayako Abe-Ouchi¹、Takashi Obase¹、Martin Werner³ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan.、2.Institute of Industrial Science, The University of Tokyo, Kashiwa, Japan.、3.Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.)

キーワード：water isotopes, sea ice, ice cores, GCM, LGM, isotope-temperature relationship

Stable water isotopes (H₂¹⁶O, H₂¹⁸O and HD¹⁶O) are integrated tracers of climate processes occurring in diverse parts of the hydrological cycle. Their measurements in polar ice cores are widely used to reconstruct temperature variations in the past, for example during the Last Glacial Maximum (LGM) ~21 000 years ago. For such reconstruction, the present-day isotope-temperature spatial gradient can be taken as a surrogate for the temporal gradient at a given site. However, this method often leads to large errors in the temperature reconstructions. The sea surface temperature (SST), the sea ice extent and the origin and transport of water vapor are factors, among many others, that influence the LGM-preindustrial isotope changes, and so the temporal isotope-temperature relationships.

In this study, we performed an ensemble of LGM simulations with the isotope-enabled atmosphere general circulation model ECHAM6-wiso [1, 2], forced with different combinations of SST and sea ice boundary forcings from the GLOMAP dataset [3], Tierney et al. [4] LGM temperature reconstruction and MIROC 4m LGM simulations [5]. We evaluated our simulation results with isotope datasets from ice cores and speleothems, and investigated the effects of prescribed changes in SST and sea ice extent on the modeled LGM-preindustrial isotope-temperature at several Antarctic and Greenland ice core sites.

[1] Cauquoin et al., Clim. Past, 15, 1913–1937, https://doi.org/10.5194/cp-15-1913-2019, 2019.
[2] Cauquoin and Werner, J. Adv. Model. Earth Syst., 13, e2021MS002532. https://doi.org/10.1029/2021MS002532, 2021.
[3] Paul et al., Clim. Past, 17, 805–824, https://doi.org/10.5194/cp-17-805-2021, 2021.
[4] Tierney et al., Nature, 584, 569–573, https://doi.org/10.1038/s41586-020-2617-x, 2020.
[5] Obase and Abe-Ouchi, Geophys. Res. Lett., 46, 11 397–11 405, https://doi.org/10.1029/2019GL084675, 2019.