Snow Nitrate Isotopes in Central Antarctica Record the Prolonged Period of Stratospheric Ozone Depletion From ∼1960 to 2000
Guitao Shi, Ye Hu, Hongmei Ma, Su Jiang, Zhenlou Chen, Zhengyi Hu, Chunlei An, Bo Sun, Meredith G. Hastings
Abstract
Abstract Interpretation of NO 3 − variability recorded in ice cores remains challenging as it can be lost from snow. Here, we present 60‐year records of NO 3 − and its isotopic composition ( δ 15 N, δ 18 O, and Δ 17 O) in snow in central Antarctica, Dome A. In the upper ∼90 cm snowpack, variations in concentration and isotopic composition of NO 3 − are dominated by photolytic loss, and δ 18 O and Δ 17 O of NO 3 − are associated with the recycling of NO x to NO 3 − in the condensed phase driven by photolysis. In the deeper snowpack (∼1960–2000), we observe prolonged trends in concentration and isotopic composition of NO 3 − , which are best explained as enhanced snow NO 3 − photolysis due to long‐term decreasing total column ozone (TCO). That is, the prolonged period of trends in NO 3 − and its isotopes in extremely low snow accumulation sites such as Dome A relay information on variations in TCO and consequently surface solar ultraviolet radiation over time.