Factors controlling the nitrate in the DT-401 ice core in eastern Antarctica

Abstract

Nitrate, an oxidized product of NO x preserved in the polar ice cores, has often been used to estimate past changes of the atmospheric nitrogen cycle. A 102.65 m ice core drilled at DT-401 (79°01′S, 77°00′E) in 1999 provides an opportunity to investigate the possible influencing factors for the nitrate budget in the eastern Antarctica. We studied the relationship between the δ 18O (representing the temperature), accumulation rate, volcanic deposition and the astronomical factors (such as the solar activities, supernovae, etc.), and the nitrate variation along the whole duration (2680-year) of the ice core. Prominent impacts of the accumulation rate acting on the nitrate flux rather than the concentration were detected. However, no significant correlation was found between the δ 18O and the nitrate deposition characteristics (concentration and the flux variations). Volcanic deposition can significantly affect the deposition of nitrate with a decreasing trend accompanied by the nss-SO4 −2 (volcanic signal) peak values. Impacts of the solar activities on the nitrate deposition can be detected at this site, and three prominent periodicities (16.6, 24.0 and 102.0 yr) were found for the nitrate concentration variations. Six climatic events (Dalton Minimum, Maunder Minimum, Sporer Minimum, Wolf Minimum, Oort Minimum and Medieval Maximum) during the past 1150 years were observed with lower nitrate values for the foregoing five events and higher value for the last one.