Brief communication: Uncertainties in Southern Ocean sea surface conditions and their impact on Antarctic climate over 1958–1978

Abstract. Atmospheric reanalyses extending before 1979, including ERA5, show a substantial cold bias over Antarctica during 1958–1978. Because Southern Ocean sea surface conditions (SSCs) are poorly constrained in this period, we assess their role using two ensembles of a global atmospheric model forced by different SSC datasets. The first uses the widely employed HadISST product, while the second is based on a recent reconstruction that assimilates continental observations. Our results show that SSC differences strongly alter the Antarctic surface climate, but explain only about 30 % of the ERA5 cold bias ERA5, indicating that additional factors contribute to this bias.