Methodology:

The Peter 1st firn core was drilled using a Kovacs hand drill in 2017, as part of the Antarctic Circumnavigation Expedition (ACE) cruise. Major ion concentrations were measured using a high-performance Dionex Integrion ion chromatograph in a class-100 cleanroom at BAS. Major ion chemistry was used to annual layer count the ice core and provide the age-scale to convert the stable water isotopes to annual averages. The snow accumulation was based on the annual layer counted layer thickness, converted to meters of water equivalent based on the measured firn density.

Isotopes, d18O, were measured using a Picarro L2130-i analyser at the British Antarctic Survey (BAS), with an accuracy of 0.3 and 0.9 per mille respectively. The measurements are reported against the international standard of Vienna Standard Mean Ocean Water (V-SMOW).

Data collection:

Dionex Integrion ion chromatograph (major ions) and Picarro L2130-i analyser (isotopes). The processing of the data, extraction, assigning depth scale, calibration, and calculation of annual means was done utilizing MATLAB version 2022b.

Data quality:

The raw data were corrected using two-point calibration, utilizing in-house reference waters. The internal standards have been calibrated with the Vienna Standard Mean Ocean Water 2 (V-SMOW2) and Standard Light Antarctic Precipitation 2 (SLAP2) reference waters.

Missing data shown as NaN.

Chemistry data presented in parts per billion (ppb).

Oxygen isotope data in per mille (ppth).

Snow accumulation data in meters water equivalent per year (m weq yr-1).