Abstract
Ice core ages have been typically determined by counting the layer boundaries of various proxies that represent annual cycles. Some studies in Greenland have identified winter and summer layers, but it is difficult to identify them at higher resolutions (several months resolution) in ice cores drilled at sites with low accumulation rates 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 snow accumulation area (1.02 m w.e. a-1) in southeast Greenland. However, the SE1 core covered for the past 60 years only. Here, we report the age scale based on δ18O data of the SE-Dome II (SE2) ice core (length: 250.79 m) drilled in 2021 in southeast Greenland. The δ18O was analyzed using a cavity ring-down spectrometer (L2130-i, Picarro) with a precision (1σ) of ±0.04‰. The SE2 core δ18O highly correlated with the SE1 core δ18O (r = 0.90), suggesting that the within-year peaks in the SE core are climatic signals. The age scale was created using the SE1 core method, but for this study, we used iso-GSM nudged to historical reanalysis data (20CRv2) for 1870-1979 and created a longer age scale. There was a high correlation between the ice core data and the model (r = 0.76), and by matching the within-year patterns (typically negative peaks during the warm season). Based on this age scale, we analyzed the day on which the maximum and minimum peaks of the mean H2O2 concentration data (Kawakami et al., 2023). The maximum and minimum of H2O2 concentrations for 1980-2020 were estimated on July 20 and January 7, respectively.   REFERENCESFurukawa, R. et al. , Seasonal-Scale Dating of a Shallow Ice Core From Greenland Using Oxygen Isotope Matching Between Data and Simulation, Journal of Geophys. Res. Atmospheres, 122, 20, 10,873-10,887, 2017, https://doi.org/10.1002/2017JD026716Kawakami, K., et al., SE-Dome II Ice Core Dating With Half-Year Precision: Increasing Melting Events From 1799 to 2020 in Southeastern Greenland, Journal of Geophys. Res.  Atmospheres, 128, 20, 2023, https://doi.org/10.1029/2023JD038874
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