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). Hydrogen peroxide in OH-9 was measured on the British Antarctic Survey (BAS) Continuous Flow Analysis (CFA) system following the methods in Grieman et al. (2022). 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.