Spatial distribution of 17O-excess in surface snow along a traverse from Zhongshan station to Dome A, East Antarctica

The influence of temperature on the triple isotopic composition of oxygen in water is still an open question and limits the interpretation of water isotopic profiles in Antarctic ice cores. The main limitation arises from the lack of O-17-excess measurements in surface snow and especially for remote regions characterized by low temperature and accumulation rate. In this study, we present new O-17-excess measurements of surface snow along an East Antarctic traverse, from the coastal Zhongshan station to the highest point of the Antarctic ice sheet at Dome A. The O-17-excess data significantly decrease inland, with a latitudinal gradient of -1.33 +/- 0.41 per meg/degree, an altitudinal gradient of -0.48 +/- 0.17 per meg/100 m, and a temperature gradient of 0.35 +/- 0.11 per meg/degrees C. Theoretical calculations performed using a Rayleigh model attribute this inland decrease to kinetic isotopic fractionation occurring during condensation from vapor to ice under supersaturation conditions at low temperatures. However, large heterogeneity of O-17-excess in Antarctic precipitation cannot only be explained by temperature at condensation and/or influences of relative humidity in the moisture source region. (C) 2015 Elsevier B.V. All rights reserved.