Abstract
Water stable isotopes (δ18O and δD) in Antarctic snow pits and ice cores are extensively applied in paleoclimate reconstruction. However, their interpretation varies over some climate change processes that can alter isotope signals after deposition, especially at sites with a low snow accumulation rate (<30 mm w.e. year−1). To investigate post-depositional effects during the archival processes of snow isotopes, we first analyzed δ18O and δD variations in summer precipitation, surface snow and snow pit samples collected at Dome A. Then, the effects of individual post-depositional processes were evaluated from the results of field experiments, spectral analysis and modeling simulations. It was found that the sublimation–condensation cycle and isotopic diffusion were likely the dominant processes that modified the δ18O at and under the snow–air interface, respectively. The sublimation–condensation cycle can cause no significant isotopic modification of δ18O from field experiments with ~3 cm snow. The diffusion process can significantly erase the original seasonal variation of δ18O driven by atmospheric temperature, leading to an apparent cycle of ~20 cm average wavelength present in the δ18O profile. Through the comparison with the artificial isotopic profile, the noise input from the diffusion process was the dominant component in the δ18O signal. Although some other processes (such as drifting, ventilation and metamorphism) were not fully considered, the quantitative understanding for the sublimation–condensation and diffusion processes will contribute to the paleoclimate construction using the ice core water isotope records at Dome A.
Highlights
Water stable isotopes (δ18 O and δD) in Antarctic ice cores can be used as an important proxy to reconstruct past temperature evolution at seasonal to orbital timescales over the Quaternary [1,2,3]
Does not remain constant over time. This temporal variability can be due to the influence of a significant noise, which interferes with the isotopic signal preserved in surface snow
This study provides new observations and modeling δ18O of precipitation, surface snow, and snow pit samples at Dome A, the summit of the Antarctic ice sheet
Summary
Water stable isotopes (δ18 O and δD) in Antarctic ice cores can be used as an important proxy to reconstruct past temperature evolution at seasonal to orbital timescales over the Quaternary [1,2,3]. Water 2020, 12, 1707 place during surface snow formation (including evaporation at moisture source, transportation, condensation, and post-deposition), this noise can be shaped by multiple effects (e.g., moisture source source, transportation, and post-deposition), this noisevapors can be shaped by multipleorigins, effects conditions, moisture condensation, transport trajectories, mixing between from different (e.g., moisture source conditions, moisture transport trajectories, mixing between vapors from different precipitation intermittency), which influence δ variations through equilibrium and kinetic origins, precipitation fractionation [8,9,10]. In the low-accumulation regions in Antarctica, processes, mechanical mixing, sublimationand andcold re-condensation, molecular post-depositional diffusion, ventilation, and including mechanical diffusion, ventilation, metamorphism (Figuremixing, 1), play sublimation an importantand rolere-condensation, in the modifyingmolecular of the original isotope signal of andupper metamorphism
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