The Dominant Role of Brewer-Dobson Circulation on 17O-Excess Variations in Snow Pits at Dome A, Antarctica

Abstract

Recent studies have suggested that water isotopologues in snow pits from remote East Antarctica can be influenced by the input of stratospheric water, which has anomalously high 17O-excess values. However, it remains unclear whether the 17O-excess records preserved in snow and ice from this region can be used to reconstruct stratosphere-troposphere exchange (STE). In this study, we present high-resolution 17O-excess records from two snow pits at Dome A, the highest point of the Antarctic ice sheet. The 17O-excess records show a significant positive correlation with the strength of the Brewer-Dobson circulation (BDC), the hemispheric-scale troposphere-stratosphere overturn circulation. Stronger BDC leads to more stratospheric water input over Antarctica and higher 17O-excess, and vice versa. In addition, the 17O-excess records also have a significant positive correlation with the Southern Annular Mode (SAM) index, because SAM modulates Antarctic precipitation, which has a dilution effect on the stratospheric water input. The 17O-excess records do not show significant correlations with local temperature and relative humidity in the moisture source region. These results suggest the dominant effect of BDC on 17O-excess and indicate the potential for using 17O-excess records in ice cores from remote sites in East Antarctica for reconstructing long-term variations of STE, and understanding their mechanisms and climate effects.