Preprints
https://doi.org/10.5194/egusphere-2023-2585
https://doi.org/10.5194/egusphere-2023-2585
21 Dec 2023
 | 21 Dec 2023

Towards an understanding of the controls on δO2/N2 variability in ice core records

Romilly Harris Stuart, Amaëlle Landais, Laurent Arnaud, Christo Buizert, Emilie Capron, Marie Dumont, Quentin Libois, Robert Mulvaney, Anaïs Orsi, Ghislain Picard, Frédéric Prié, Jeffery Severinghaus, Barbara Stenni, and Patricia Martinerie

Abstract. Processes controlling pore closure are broadly understood yet defining the physical mechanisms controlling associated elemental fractionation remains ambiguous. Previous studies have shown that the pore closure process leads to a decrease in concentration of small-size molecules (e.g., H2, O2, Ar, Ne, He) in the trapped bubbles. Ice core δ(O2/N2) records – the ratio of O2 to N2 molecules in bubbles trapped in ice cores relative to the atmosphere – are therefore depleted owing to this O2 loss and show a clear link with local summer solstice insolation making it a useful dating tool. In this study, we compile δ(O2/N2) records from 14 polar ice cores and show a new link between δ(O2/N2) and local surface temperature and/or accumulation rate, in addition to the influence of the summer solstice insolation. We argue that both local climate-driven and insolation forcings are linked to the modulation of snow physical properties near the surface. Using the Crocus snowpack model, we perform sensitivity tests to identify the response of near-surface snow properties to changes in insolation, accumulation rate, and air temperature. These tests support a mechanisms linked to snow grain size, such that the larger the grain size for a given density, the stronger the pore closure fractionation, and hence, lower δ(O2/N2) values. Our findings suggest that local accumulation rate and temperature should be considered when interpreting δ(O2/N2) as an insolation proxy.

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Romilly Harris Stuart, Amaëlle Landais, Laurent Arnaud, Christo Buizert, Emilie Capron, Marie Dumont, Quentin Libois, Robert Mulvaney, Anaïs Orsi, Ghislain Picard, Frédéric Prié, Jeffery Severinghaus, Barbara Stenni, and Patricia Martinerie

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2585', Anonymous Referee #1, 26 Jan 2024
    • AC1: 'Reply on RC1', Romilly Harris Stuart, 06 Mar 2024
  • RC2: 'Comment on egusphere-2023-2585', Jochen Schmitt, 26 Jan 2024
    • AC2: 'Reply on RC2', Romilly Harris Stuart, 06 Mar 2024
    • AC3: 'Reply on RC2', Romilly Harris Stuart, 06 Mar 2024
Romilly Harris Stuart, Amaëlle Landais, Laurent Arnaud, Christo Buizert, Emilie Capron, Marie Dumont, Quentin Libois, Robert Mulvaney, Anaïs Orsi, Ghislain Picard, Frédéric Prié, Jeffery Severinghaus, Barbara Stenni, and Patricia Martinerie
Romilly Harris Stuart, Amaëlle Landais, Laurent Arnaud, Christo Buizert, Emilie Capron, Marie Dumont, Quentin Libois, Robert Mulvaney, Anaïs Orsi, Ghislain Picard, Frédéric Prié, Jeffery Severinghaus, Barbara Stenni, and Patricia Martinerie

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Short summary
The influence of local accumulation rate and temperature on δO2/N2 ice core records, a key dating tool, are not fully understood, but required for a full mechanistic understanding. We show evidence that mean δO2/N2 is strongly dependent on local accumulation rate and temperature, in addition to the well documented insolation dependence. Snowpack modelling is used to investigate which physical properties drive the mechanistic dependence on these local parameters.