Open AccessFactors controlling nitrate in ice cores: Evidence from the Dome C deep ice core
Author(s) -
Röthlisberger Regine,
Hutterli Manuel A.,
Sommer Stefan,
Wolff Eric W.,
Mulvaney Robert
Publication year - 2000
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jd900264
Subject(s) - ice core , nitrate , snow , geology , glacial period , atmospheric sciences , cryosphere , holocene , deposition (geology) , polar front , oceanography , firn , environmental science , sea ice , geomorphology , chemistry , sediment , organic chemistry
In order to estimate past changes in atmospheric NO x concentration, nitrate, an oxidation product of NO x , has often been measured in polar ice cores. In the frame of the European Project for Ice Coring in Antarctica (EPICA), a high‐resolution nitrate record was obtained by continuous flow analysis (CFA) of a new deep ice core drilled at Dome C. This record allows a detailed comparison of nitrate with other chemical trace substances in polar snow under different climatic regimes. Previous studies showed that it would be difficult to make firm conclusions about atmospheric NO x concentrations based on ice core nitrate without a better understanding of the factors controlling NO 3 − deposition and preservation. At Dome C, initially high nitrate concentrations (over 500 ppb) decrease within the top meter to steady low values around 15 ppb that are maintained throughout the Holocene ice. Much higher concentrations (averaging 53 ppb) are found in ice from the Last Glacial Maximum (LGM). Combining this information with data from previous sampling elsewhere in Antarctica, it seems that under climatic conditions of the Holocene, temperature and accumulation rate are the key factors determining the NO 3 − concentration in the ice. Furthermore, ice layers with high acidity show a depletion of NO 3 − , but higher concentrations are found before and after the acidity layer, indicating that NO 3 − has been redistributed after deposition. Under glacial conditions, where NO 3 − shows a higher concentration level and also a larger variability, non‐sea‐salt calcium seems to act as a stabilizer, preventing volatilization of NO 3 − from the surface snow layers.