On the relationship between δO2∕N2 variability and ice sheet surface conditions in Antarctica

Autor: R. Harris Stuart, A. Landais, L. Arnaud, C. Buizert, E. Capron, M. Dumont, Q. Libois, R. Mulvaney, A. Orsi, G. Picard, F. Prié, J. Severinghaus, B. Stenni, P. Martinerie
Jazyk: angličtina
Rok vydání: 2024
Předmět:
Zdroj: The Cryosphere, Vol 18, Pp 3741-3763 (2024)
Druh dokumentu: article
ISSN: 1994-0416
1994-0424
DOI: 10.5194/tc-18-3741-2024
Popis: While the processes controlling pore closure are broadly understood, the physical mechanisms driving the associated elemental fractionation remains ambiguous. Previous studies have shown that the pore closure process leads to a depletion in small-sized molecules (e.g. H2, O2, Ar, Ne, He) in ice core bubbles relative to larger-sized molecules like N2. This size-dependent fractionation, identified using ice core δ(O2/N2) records, exhibits a clear anti-correlation with local summer solstice insolation, making δ(O2/N2) a valuable ice core dating tool. Mechanisms controlling this relationship are attributed to the physical properties of deep firn. In this study, we compile δ(O2/N2) records from 15 polar ice cores and show a new additional link between δ(O2/N2) and local surface temperature and/or accumulation rate. Using the Crocus snowpack model, we perform sensitivity tests to identify the response of near-surface snow properties to changes in insolation intensity, accumulation rate, and air temperature. These tests support a mechanism linked to firn grain size, such that the larger the grain size for a given density, the stronger the pore closure fractionation and, hence, the lower the δ(O2/N2) values archived in the ice. Based on both snowpack model outputs and data compilation, our findings suggest that local accumulation rate and temperature should be considered when interpreting δ(O2/N2) as a local insolation proxy.
Databáze: Directory of Open Access Journals
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