WAIS Divide Ice Core δ 15 N(NO 3 − ) Variability Over the Last Glacial‐Interglacial Cycle: Controlling Factors and Implications for Retrieving Surface Mass Balance Using Ice Core δ 15 N(NO 3 − ) Records

作者：Zhuang Jiang, Becky Alexander, Joseph R. McConnell, Andrew J. Schauer, Lei Geng · 发表于：Journal of Geophysical Research Atmospheres · 年份：2025 · DOI：10.1029/2025jd043712 · 被引用次数：1 · 研究领域：Geology and Paleoclimatology Research、Isotope Analysis in Ecology、Atmospheric and Environmental Gas Dynamics

Abstract Ice core nitrate can serve as a valuable tracer for past atmospheric nitrogen oxide (NO x ) and oxidant concentrations. However, photolysis‐driven postdepositional processing can alter ice core nitrate signals and complicate their interpretation. We present a new nitrogen isotope ( δ 15 N) record of nitrate measured in the West Antarctic Ice Sheet (WAIS) Divide ice core covering the last glacial period and Holocene. The glacial δ 15 N(NO 3 − ) is substantially higher than the Holocene δ 15 N(NO 3 − ), with a glacial‐interglacial difference of (26.6 ± 5.7) ‰. All samples exhibit a strong negative correlation between δ 15 N(NO 3 − ) and the snow accumulation rate, suggesting that postdepositional processing is the primary driver of the δ 15 N(NO 3 − ) variability. Photochemical model calculations indicate that changes in the degree of postdepositional processing can fully explain the observed glacial‐interglacial δ 15 N(NO 3 − ) difference, with 12.7% and 31.8% of nitrate mass loss during the Holocene and glacial climate, respectively. Comparison with the Greenland GISP2 δ 15 N(NO 3 − ) record indicates that the glacial level of postdepositional modification was higher at WAIS Divide despite its snow accumulation rate was twice that at Summit, Greenland. This is due to the higher light‐absorbing impurity contents in the GISP2 ice core that reduced postdepositional losses. We also assess the ability of using δ 15 N(NO 3 − ) for past surface mass balance (SMB) reconstruc...