Acquisition of Post-Depositional Effects on Stable Isotopes (δ 18 O and δD) of Snow and Firn at Dome A, East Antarctica

• Published in: Water
• Main Authors: Tianming Ma, Li Li, Guitao Shi, Yuansheng Li
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: water stable isotopes; post-depositional process; sublimation–condensation cycle; diffusion; surface snow; Hydraulic engineering; TC1-978; Water supply for domestic and industrial purposes; TD201-500; Antarctic; East Antarctica; Antarc*; Antarctica; ice core
• Online Access: https://doi.org/10.3390/w12061707; https://doaj.org/article/1ffc63e5084643d2a41a7cd867c9beb8

Water stable isotopes (δ 18 O 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 δ 18 O 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 δ 18 O at and under the snow–air interface, respectively. The sublimation–condensation cycle can cause no significant isotopic modification of δ 18 O from field experiments with ~3 cm snow. The diffusion process can significantly erase the original seasonal variation of δ 18 O driven by atmospheric temperature, leading to an apparent cycle of ~20 cm average wavelength present in the δ 18 O profile. Through the comparison with the artificial isotopic profile, the noise input from the diffusion process was the dominant component in the δ 18 O 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.