Contribution of the Southern Annular Mode to variations in water
isotopes of daily precipitation at Dome Fuji, East Antarctica
Abstract
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 δ18O of precipitation (δ18Op) at Dome Fuji, East
Antarctica. The Southern Annular Mode (SAM), the primary mode of
atmospheric circulation in the southern mid-high latitudes,
significantly contributes to the isotope signals. Positive δ18Op
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 δ18Op 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.