Preprints
https://doi.org/10.5194/cp-2023-96
https://doi.org/10.5194/cp-2023-96
05 Dec 2023
 | 05 Dec 2023
Status: this preprint is currently under review for the journal CP.

Drivers of late Holocene ice core chemistry in Dronning Maud Land: The context for the ISOL-ICE project

V. Holly L. Winton, Robert Mulvaney, Joel Savarino, Kyle R. Clem, and Markus M. Frey

Abstract. Quantifying the natural variability of the stratospheric ozone layer and understanding the underlying factors that control natural total column ozone (TCO) variability are required to put modern observations into historical context and evaluate the effectiveness of climate and TCO protection policies. Within the framework of the Isotopic Constraints on Past Ozone Layer in Polar Ice (ISOL-ICE) project, we present initial ice core results from the new ISOL-ICE ice core covering the last millennium from the high-elevation Dronning Maud Land (DML) located under the Antarctic spring stratospheric TCO minimum, and discuss the implications for interpreting the stable isotopic composition of nitrogen in ice core nitrate (δ15N(NO3-)) as a surface ultra-violet radiation (UV) and TCO proxy. To interpret the ice core δ15N(NO3-) record, an understanding of past snow accumulation changes, as well as aerosol source regions and present-day drivers of their variability are required. We therefore report here the ice core age-depth model, the snow accumulation and ice chemistry records, and correlation analysis of these records with climate variables over the observational era (1979–2016). The ISOL-ICE ice core covers the last 1349 years from 668 to 2017 C.E. ± 3 years extending previous ice core records from the region by two decades and shows excellent reproducibility with those records. The extended ISOL-ICE record of last two decades showed a continuation of the methanesulphonate (MSA) increase from ~1800 to present while there were less frequent large deposition events of sea salts relative to the last millennium. The correlation analysis, combined with the finding that sea salts do not carry a sea ice signature to the site, highlight that sea salt and MSA aerosol concentrations are primarily related to atmospheric transport over the extended two-decade period and not to changes in sea ice source strength. Correlation of the snow accumulation record with climate variables over the observational era showed that precipitation at ISOL-ICE is predominately derived from the South Atlantic with onshore winds delivering marine air masses to the site. The snow accumulation rate was stable over the last millennium with no notable trends over last two decades relative to the last millennium. Interannual variability in the accumulation record, ranging between 2 and 20 cm a−1 (w.e.), would influence the ice core δ15N(NO3-) record. The mean snow accumulation rate of 6.5 ± 2.4 cm a-1 (w.e.) falls within the range suitable for reconstructing surface mass balance from ice core δ15N(NO3-) highlighting that the ISOL-ICE ice core δ15N(NO3-) can be used to reconstruct either the snow accumulation rate or surface UV if the ice core δ15N(NO3-) is corrected for the snow accumulation influence.

V. Holly L. Winton, Robert Mulvaney, Joel Savarino, Kyle R. Clem, and Markus M. Frey

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-96', Anonymous Referee #1, 16 Jan 2024
  • RC2: 'Comment on cp-2023-96', Tessa Vance, 09 Feb 2024
V. Holly L. Winton, Robert Mulvaney, Joel Savarino, Kyle R. Clem, and Markus M. Frey
V. Holly L. Winton, Robert Mulvaney, Joel Savarino, Kyle R. Clem, and Markus M. Frey

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Short summary
In 2018, a new 120 m ice core was drilled in a region located under the Antarctic ozone hole. We present the first results including a 1300-year record of snow accumulation and aerosol chemistry. We investigate the aerosol and moisture source regions and atmospheric processes related to the ice core record and discuss what this means for developing a record of past ultraviolet-radiation and ozone depletion using the stable isotopic composition of nitrate measured in the same ice core.