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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2018-518
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-518
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 22 Jan 2019

Research article | 22 Jan 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Highly branched isoprenoids for Southern Ocean semi-quantitative sea ice reconstructions: a pilot study from the Western Antarctic Peninsula

Maria-Elena Vorrath1, Juliane Müller1,2,3, Oliver Esper1, Gesine Mollenhauer1,2, Christian Haas1, Enno Schefuß2, and Kirsten Fahl1 Maria-Elena Vorrath et al.
  • 1Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany
  • 3Department of Geosciences, University of Bremen, Germany

Abstract. Organic geochemical and micropaleontological analyses of surface sediments collected in the southern Drake Passage and the Bransfield Strait, Antarctic Peninsula, enable a proxy-based reconstruction of recent sea ice conditions in this climate sensitive area. The distribution of the sea ice biomarker IPSO25 supports earlier suggestions that the source diatoms seem to be common in near-coastal environments characterized by an annually recurring sea ice cover. We here propose and evaluate the combination of IPSO25 with a more unsaturated highly branched isoprenoid alkene and phytosterols and introduce the PIPSO25 index as a potentially semi-quantitative sea ice proxy. This organic geochemical approach is complemented with diatom data. PIPSO25 sea ice estimates are used to discriminate between areas characterized by permanently ice-free conditions, seasonal sea ice cover and extended sea ice cover. These trends are consistent with satellite sea ice data and winter sea ice concentrations estimated by diatom transfer functions. Minor offsets between proxy-based and satellite-based sea ice data are attributed to the different time intervals recorded within the sediments and the instrumental records from the study area, which experienced rapid environmental changes during the past 100 years.

Maria-Elena Vorrath et al.
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Maria-Elena Vorrath et al.
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Highly branched isoprenoids and sterols in surface sedimentsfrom southern Drake Passage and the Bransfield Strait, Antarctic Peninsula, sampled during POLARSTERN cruise PS97 (ANT-XXXI/3) M.-E. Vorrath, J. Müller, O. Esper, G. Mollenhauer, C. Haas, E. Schefuß, and K. Fahl https://doi.pangaea.de/10.1594/PANGAEA.897162

Maria-Elena Vorrath et al.
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Short summary
The study highlights new approaches in the investigation of past sea ice in Antarctica to reconstruct the climate conditions in earth's history and reveal its future development under global warming. We examined the distribution of organic remains from different algae at the Western Antarctic Peninsula and compared it to fossil and satellite records. We evaluated IPSO25 – the sea ice proxy for the Southern Ocean with 25 carbon atoms – as a useful tool for sea ice reconstructions in this region.
The study highlights new approaches in the investigation of past sea ice in Antarctica to...
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