Firn cores OH-9 and OH-12 were retrieved from Plateau Laclavere, a small ice cap on the northernmost end of the Antarctic Peninsula. OH-9 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). OH-12 was drilled in January 2016 to a depth of 19.93 m at about 1090 m a.s.l. using a portable solar-powered and electrically operated ice-core drill (Backpack Drill; icedrill.ch AG). 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). Hydrogen peroxide in OH-9 was measured on the BAS Continuous Flow Analysis (CFA) system following the methods in Grieman et al. (2022). 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 (1979). Glacio-chemical parameters in OH-12 (calcium, chlorine, strontium, dysprosium, cerium, lanthanum) were determined at the Trace Chemistry Laboratory of the Desert Research Institute (DRI) in Reno, Nevada, USA, in summer 2017 using two Thermo Finnigan Element2 High Resolution-Inductively Coupled Plasma-Mass Spectrometry (HR-ICP-MS) instruments connected to a CFA system as described by Röthlisberger et al. (2000) and McConnell et al. (2002). Both cores were 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. OH-12 covers the period from July 2011 to January 2016. The data has been used in connection with the stable water isotope composition of the two cores (doi:10.1594/PANGAEA.871083; doi:10.1594/PANGAEA.939718) to identify moisture source regions and their temporal changes for the northern Antarctic Peninsula.