High-resolution sea-salt sodium data of firn core OH-9 from Plateau Laclavere, northern Antarctic Peninsula

Firn core OH-9 was retrieved from Plateau Laclavere, a small ice cap on the northernmost end of the Antarctic Peninsula. It was drilled in January 2014 to a depth of 11.65 m at about 1130 m above sea level (a.s.l.) using a mechanical 9 cm diameter drilling device (Rufli auger). Major ions in OH-9 (sodium, chlorine, calcium, methane sulfonic acid) were determined at the Ice Chemistry Laboratory of the British Antarctic Survey (BAS) in Cambridge, UK, using a Dionex reagent-free ion chromatography system (ICS-2000). Values of sea-salt sodium (ssNa) were calculated from sodium concentrations applying the approach of Röthlisberger et al. (2002) and Sigl et al. (2013) and using relative abundances from Bowen (Bowen, 1979). The core was dated using annual layer counting of hydrogen peroxide measurements. We additionally accounted for precipitation intermittency at the drill site by using precipitation data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 Reanalysis extracted from the grid point closest to the firn-core drill sites. OH-9 covers the period from August 2011 to January 2014.