[A-CC27] Ice cores and paleoenvironmental modeling

[ACC27-P01] Seasonal Age Scale and Intra-annual Pattern of Oxygen Isotope Record from SE-Dome II Ice core, Greenland

*SAAYA HAMAMOTO¹, Kaoru Kawakami², Mahiro Sasage^2,3, Mai Matsumoto^2,3, Bong Hayoung⁶, Kei Yoshimura⁴, Atsushi Okazaki⁵, Sumito Matoba², Yoshinori Iizuka², Ryu Uemura¹ (1.Graduate School of Environmental Studies, Nagoya University, 2.Institute of Low Temperature Science, Hokkaido University, 3.Graduate School of Environmental Science, Hokkaido University, 4.Atmosphere and Ocean Research Institute, The University of Tokyo, 5.Institute of Advanced Academic Research, Chiba University, 6.Institute of Industrial Science, The University of Tokyo)

Keywords:Ice core, Oxygen isotope

Ice cores have generally been dated by counting the layer boundaries of various proxies representing the annual cycle. Several studies in Greenland have identified winter and summer layers, but ice cores drilled at sites with low recharge rates are difficult to identify at high resolution (multi-month resolution) due to diffusion. Furukawa et al. (2017) proposed a precise age model by matching the oxygen isotope (δ¹⁸O) pattern of precipitation isotope between ice core record and isotope-incorporated general circulation models. They applied this dating method to the SE-Dome I (SE1) ice core drilled from a high accumulation area (1.02 m w.e. a^-1) in southeast Greenland. However, the SE1 core covered only the past 60 years. Here we report an age scale based on δ¹⁸O data for the SE-Dome II (SE2) ice core (length: 250.79 m) drilled in southeast Greenland in 2021. The SE2 core δ¹⁸O is highly correlated (r = 0.90) with the SE1 core δ¹⁸O, suggesting that the intra-annual peak in the SE core is a climatic signal. Although the age scale was created using the SE1 core methodology, a longer age scale was created in this study using iso-GSM nudged to the historical reanalysis data (20CRv2) for the period 1871-1979. There was a high correlation between the ice core data and the model (r = 0.76), matching the intra-annual pattern (typically, warm season negative peak). In order to figure out the cause of this intra-annual pattern, we analysed the isotopic variations during summer. The results suggest that on days when a negative peak occurs during the warm season, a low pressure developing southeast of the SE-Dome changes water vapor origin from North Atlantic Ocean to continental North America, resulting in low δ¹⁸O precipitation.