The mixing ratio and bulk isotopic composition of nitrous oxide (N2O) was measured after wet extraction and purification of the air enclosed in 150 g ice core samples from EDC, EDML, Vostok, TALDICE, and NGRIP, following the analysis procedure described in Schmitt et al. (2014). The position-specific isotopic composition of N2O was measured after dry extraction and purification of the air enclosed in 600 g ice core samples from Vostok and Taylor Glacier, following the analysis procedure described in Menking et al. (2025). The mixing ratio and isotopic composition of in situ N2O – i.e., the fraction of N2O produced in the ice – was calculated using a mass balance approach (Soussaintjean et al., preprint). After gas extraction, the sample meltwater and ice chips were collected to measure the isotopic composition of nitrate (NO3-) following the bacterial denitrification method described in Erbland et al. (2013). Each sample was associated with its ice age and gas age based on the AICC2023 chronology (Bouchet et al., 2023) for EDC, EDML, Vostok, TALDICE, and NGRIP and Baggenstos et al. (2017, 2018) for Talyor Glacier. The samples cover the periods 11 – 26 ka, 41 – 75 ka, and 136 – 143 ka. Taylor Glacier is a horizontal core, meaning the age of the ice varies with distance along a transect close to the surface where the horizontal stratigraphy is preserved (Baggenstos et al., 2017).
The compilation combines measurements of nitrate δ¹⁵N (vs Air N₂) and δ¹⁸O (vs VSMOW) from the global ocean together with ancillary hydrographic and biogeochemical measurements when available, including temperature, salinity, dissolved oxygen, nitrate, nitrite, phosphate, silicate, and ammonium concentrations.
The database contains 3410 stations, including 29779 nitrate δ¹⁵N measurements and 26633 nitrate δ¹⁸O measurements. Associated metadata include cruise identifiers, bibliographic references, Digital Object Identifiers (DOIs) linking datasets to the original studies whenever available, latitude, longitude, cruise start and end dates, sampling date, and sampling depth.
This compilation also includes most nitrate δ¹⁵N measurements reported in Rafter et al. (2019; n = 12277) and Fripiat et al. (2021; n = 15300), together with an expanded collection of nitrate δ¹⁸O measurements.