A 60-year atmospheric nitrate isotope record from a Southeast Greenland ice core with minimal post-depositional alteration

Abstract. Stable isotopes of atmospheric nitrate (NO₃⁻) are valuable tools for tracing nitrogen sources and processes; however, their signals in ice core records are often disrupted by post-depositional processes. The ice core from the southeastern Dome (SE-Dome) in Greenland is a potential record of variations in atmospheric chemistry that has experienced less post-depositional effects owing to a high accumulation rate (~1 m w e a⁻¹). Herein, we report 60-year (1959–2014) δ¹⁵N(NO₃⁻) and Δ¹⁷O(NO₃⁻) records from the SE-Dome ice core. δ¹⁵N(NO₃⁻) decreased from 1960 to 1974 and exhibited clear seasonal changes (high in summer and low in winter). Δ¹⁷O(NO₃⁻) did not exhibit any significant long-term trends, but did contain seasonal patterns. The mass-weighted annual average of δ¹⁵N(NO₃⁻) values in the SE-Dome core were 4.2 ± 2.8 ‰ lower than those in the Greenland Summit ice core between 1959–2006. The Transfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) model under the SE-Dome condition estimated changes of only 0.9 ‰ in δ¹⁵N(NO₃⁻) and −0.2 ‰ in Δ¹⁷O(NO₃⁻) from the initial deposition. Although differences in the source of NO₃⁻ cannot be discounted, the lower δ¹⁵N(NO₃⁻) values observed at the SE-Dome compared to the Summit were likely due to reduced post-depositional alteration. Therefore, the SE-Dome ice core NO₃⁻ record offers a precise reconstruction of NO_x emissions and atmospheric oxidation chemistry during transport, preserving records from both North America and Western Europe, thereby providing reliable insight into atmospheric nitrogen cycling.