Contribution of the Southern Annular Mode on variations in water
isotopes of daily precipitation at Dome Fuji, East Antarctica
Abstract
Water isotopes measured in Antarctic ice cores allow 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. This study adopted an isotope-enabled atmospheric general
circulation model for the period from 1981 to 2010 to investigate
variations in climatic factors in δ18O of
precipitation (δ18Op) at Dome Fuji,
East Antarctica. The results show that 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. It is also suggested that the isotope signals driven
by the SAM are a locational feature of Dome Fuji, related to the
asymmetric component of the SAM.