Contribution of the Southern Annular Mode to Variations in Water Isotopes of Daily Precipitation at Dome Fuji, East Antarctica

Water isotopes measured in Antarctic ice cores enable reconstruction at the first order of the past temperature variations. However, the seasonality of the precipitation and episodic events, including synoptic-scale disturbances, influence the isotopic signals recorded in ice cores. In this study, we adopted an isotope-enabled atmospheric general circulation model from 1981 to 2010 to investigate variations in climatic factors in delta O-18 of precipitation (delta O-18(p)) at Dome Fuji, East Antarctica. The Southern Annular Mode (SAM), the primary mode of atmospheric circulation in the southern midhigh latitudes, significantly contributes to the isotope signals. Positive delta O-18(p) anomalies, especially in the austral winter, are linked to the negative polarity of the SAM, which weakens westerly winds and increases the southward inflow of water vapor flux. Daily variations in temperature and delta O-18(p) in Dome Fuji are significantly small in the austral summer, and their contribution to the annual signals is limited. The isotope signals driven by the SAM are a locational feature of Dome Fuji, related to the asymmetric component of the large-scale atmospheric pattern.

Automated summary

Water isotopes in Antarctic ice cores provide key insights into past temperature variations, but are influenced by precipitation seasonality and episodic events. The Southern Annular Mode (SAM) significantly contributes to isotopic signals, with positive anomalies in the austral winter related to SAM's negative polarity. Daily temperature and isotopic variations in Dome Fuji are minimal in the austral summer, with SAM-driven isotopic signals being a locational feature related to large-scale atmospheric patterns.