Instrument- and Tree-Ring-Based Estimates of the Antarctic Oscillation

Abstract

Abstract An estimate of the strength of the austral summer Antarctic Oscillation using station sea level pressure records for the period 1878–2000 is presented, the first to the authors' knowledge. The reconstruction was obtained by relating the Antarctic Oscillation (AAO) intensity derived from NCEP–NCAR reanalysis data to the leading principal components of station records using multiple regression analysis. Particular effort has been made to fit the model in a way that is robust to the questionable trends in the NCEP–NCAR data in the Southern Hemisphere. The trends in the reconstruction are derived from the station data, not from the NCEP data. Cross-validation with the NCEP data and comparison with other analyses of the AAO over the late instrumental period give confidence that this station-based reconstruction can be regarded as trustworthy. With regard to the whole reconstruction period, some unquantifiable uncertainty stems from potential instability of the statistical relationships. To extend this...