An annually resolved chronology for the Mount Brown South ice cores, East Antarctica.

Climate reconstructions of the last millennium rely on networks of high resolution and well-dated proxy records. This study presents age-at-depth data and preliminary results from the new Mount Brown South ice cores, collected at an elevation of 2,084 metres on the boundary of Princess Elizabeth and Kaiser Wilhelm II Land in East Antarctica. We show an initial analysis of the site meteorology, mean annual chemical species concentrations, and seasonal cycles including analysis of a seasonal cycle in fluoride concentrations with a potential link to sea ice formation. The annually resolved chronologies were developed from this data using a site-specific layer-counting methodology which employed seasonally varying trace chemical species and water isotope ratios, combined with a volcanic horizon alignment approach. The chronologies developed include the 'Main' 295 m record spanning 1,137 years (873-2009 CE), and three surface cores spanning the most recent 39-52 years up to the surface age at the time of drilling (austral summer 2017/2018). Mean annual trace chemical concentrations are compared to the Law Dome ice core further to the east and discussed in terms of atmospheric transport, and the uncertainty in the determination of annual horizons via layer counting is quantified. The MBS chronologies presented here - named MBS2023 - will underpin the development of new palaeoclimate records spanning the past millennium from this under-represented region of East Antarctica. [ABSTRACT FROM AUTHOR]