Diagnoses of Antarctic Inland Water Cycle Regime: Perspectives From Atmospheric Water Vapor Isotope Observations Along the Transect From Zhongshan Station to Dome A

Abstract

Water stable isotopes are crucial for paleoclimate reconstruction and water cycle tracing in Antarctica. Accurate measurement of atmospheric water vapor isotopic composition of hydrogen and oxygen is required urgently for understanding the processes controlling the atmosphere–snow interaction and associated isotope fractionation. This study presents in situ real-time measurements of water vapor isotopes along the transect from Zhongshan Station to Dome Argus (hereafter Dome A) in East Antarctica for the first time. The results reveal that the surface vapor stable isotopes of δ18O and δ D showed a gradual decreasing trend in the interior plateau region with the distance away from the coast, with significant δ18O-temperature correlation gradient of 1.61‰°/C and δ18O-altitude gradient of –2.13‰/100 m. Meanwhile, d-excess gradually arises with elevation rise. Moreover, the spatial variation of vapor isotopic composition displays three different characters implying different atmosphere circulation backgrounds controlling the inland water cycle; it can be divided as the coastal steep area below 2,000 m, a vast inland area with an elevation varied between 2,000 and 3,000 m, and high central plateau. Thirdly, observed high inland Antarctica water vapor d-excess quantitatively confirms stratosphere air intrusion and vapor derived from low latitudes by Brewer–Dobson circulation. Finally, the diurnal cycle signals of interior area water vapor isotopes δ18O, δ D, and air temperature highlighted the substantial domination of the supersaturation sublimation/condensation effect in inland, and this suggests that fractionation occurs during sublimation and vapor–snow exchanges should no longer be considered insignificant for the isotopic composition of near-surface snow in Antarctica.