Dating of an East Antarctic ice core (GV7) by high resolution chemical stratigraphies

Ice core dating is the first step for a correct interpretation of climatic and environmental changes. In this work, we release a stratigraphic dating of the uppermost 197 m of the 250 m deep GV7(B) ice core (drilling site, 70°41’S, 158°52’E, 1950 m a.s.l.) with a sub-annual resolution. Chemical stratigraphies of NO3−, MSA (methanesulfonic acid), non-sea salt SO42−, sea-salt ions and the oxygen isotopic composition (δ18O) were used in the annual layer counting upon the identification of a seasonal profile in their records. Different procedures were tested and thanks to the volcanic history of the core, obtained in previous works, an accurate age-depth correlation was obtained for the period 1179–2009 CE. Once the dating of the core was finalized, the annual mean accumulation rate was evaluated throughout the analyzed 197 m of the core, obtaining an annually resolved history of the snow accumulation on site in the last millennium. A small, yet consistent, rise in accumulation rate was found for the last 830 years since the middle of the 18th century.