11:30 〜 11:45
[ACC33-10] Atmospheric nitrate isotope record from a SE-Dome ice core with minimal post-depositional alteration
キーワード：アイスコア、硝酸、同位体、質量非依存分別
Stable isotopes of atmospheric nitrate (NO3−) serve as valuable tracers for nitrogen sources and atmospheric processes. However, post-depositional processes often alter their signals in ice core records. The Southeastern Dome (SE-Dome) ice core in Greenland presents a promising archive of atmospheric chemistry variations, as it has experienced minimal post-depositional modification due to its high accumulation rate (~1 m w.e. a−1).
In this study, we present a 60-year (1959–2014) record of δ15N(NO3−) and Δ17O(NO3−) from the SE-Dome ice core. δ15N(NO3−) exhibited a decline from 1960 to 1974 and displayed clear seasonal variations, with higher values in summer and lower values in winter. Δ17O(NO3−) showed no significant long-term trend but retained a distinct seasonal pattern. The mass-weighted annual mean δ15N(NO3−) values at SE-Dome were, on average, 4.2 ± 2.8 ‰ lower than those observed in the Greenland Summit ice core between 1959 and 2006.
Using the Transfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) model under SE-Dome conditions, post-depositional changes were estimated to be limited, with only a 0.9 ‰ shift in δ15N(NO3−) and a −0.2 ‰ shift in Δ17O(NO3−) from initial deposition. While differences in NO3− sources cannot be entirely ruled out, the lower δ15N(NO3−) values at SE-Dome compared to Summit likely reflect reduced post-depositional processing.
As a result, the SE-Dome ice core NO3− record provides a more direct reconstruction of NOx emissions and atmospheric oxidation chemistry during transport. This record captures signals from both North American and Western European sources, offering robust insights into past atmospheric nitrogen cycling. In this presentation, we will introduce the latest findings on the controlling factors of δ15N(NO3−) and discuss future prospects for what can be revealed from the SE-Dome's nitrate isotope record.
In this study, we present a 60-year (1959–2014) record of δ15N(NO3−) and Δ17O(NO3−) from the SE-Dome ice core. δ15N(NO3−) exhibited a decline from 1960 to 1974 and displayed clear seasonal variations, with higher values in summer and lower values in winter. Δ17O(NO3−) showed no significant long-term trend but retained a distinct seasonal pattern. The mass-weighted annual mean δ15N(NO3−) values at SE-Dome were, on average, 4.2 ± 2.8 ‰ lower than those observed in the Greenland Summit ice core between 1959 and 2006.
Using the Transfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) model under SE-Dome conditions, post-depositional changes were estimated to be limited, with only a 0.9 ‰ shift in δ15N(NO3−) and a −0.2 ‰ shift in Δ17O(NO3−) from initial deposition. While differences in NO3− sources cannot be entirely ruled out, the lower δ15N(NO3−) values at SE-Dome compared to Summit likely reflect reduced post-depositional processing.
As a result, the SE-Dome ice core NO3− record provides a more direct reconstruction of NOx emissions and atmospheric oxidation chemistry during transport. This record captures signals from both North American and Western European sources, offering robust insights into past atmospheric nitrogen cycling. In this presentation, we will introduce the latest findings on the controlling factors of δ15N(NO3−) and discuss future prospects for what can be revealed from the SE-Dome's nitrate isotope record.