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Climate of the Past An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/cp-2020-63
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2020-63
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  12 May 2020

12 May 2020

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This preprint is currently under review for the journal CP.

Sea Ice dynamics at the Western Antarctic Peninsula during the industrial era: a multi-proxy intercomparison study

Maria-Elena Vorrath1, Juliane Müller1,2,3, Lorena Rebolledo4,5, Paola Cárdenas4, Xiaoxu Shi1, Oliver Esper1, Thomas Opel1, Walter Geibert1, Práxedes Muñoz6, Christian Haas1, Carina B. Lange4,7,8,9, Gerrit Lohmann1, and Gesine Mollenhauer1,2 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
  • 4Centro de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Valdivia, Chile
  • 5Instítuto Antártico Chileno (INACH), Punta Arenas, Chile
  • 6Facultad de Ciencias del Mar, Universidad Católica del Norte, Coquimbo, Chile
  • 7Centro Oceanográfico COPAS Sur-Austral, Universidad de Concepción, Chile
  • 8Departamento de Oceanografía, Universidad de Concepción, Chile
  • 9Scripps Institution of Oceanography, La Jolla, CA 92037, USA

Abstract. In the last decades, changing climate conditions have had a severe impact on sea ice at the Western Antarctic Peninsula (WAP), an area rapidly transforming under global warming. To study the development of spring sea ice and environmental conditions in the pre-satellite era we investigated three short marine sediment cores for their biomarker inventory with particular focus on the sea ice proxy IPSO25 and micropaleontological proxies. The core sites in the Bransfield Strait are located in shelf to deep basin areas characterized by a complex oceanographic frontal system, coastal influence and sensitivity to large-scale atmospheric circulation patterns. We analyzed geochemical bulk parameters, biomarkers (highly branched isoprenoids, glycerol dialkyl glycerol tetraethers, sterols), and diatom abundances and diversity over the past 200 years (210Pb dating), and compared them to observational data, sedimentary and ice core climate archives as well as results from numerical models. Based on biomarkers we could identify four different stratigraphic units with (1) stable conditions and moderate sea ice cover before 1860, (2) low to moderate sea ice cover between 1860 and 1930, (3) high seasonal variability and changes in sea ice regimes from 1930 to 1990 and (4) a shift to increasing sea ice cover despite anthropogenic warming since 1990. Although IPSO25 concentrations correspond quite well with satellite sea ice observations for the past 40 years, we note discrepancies between the biomarker-based sea ice estimates and the long-term model output for the past 200 years, ice core records and reconstructed atmospheric circulation patterns such as El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM). We propose that the sea ice biomarker proxies IPSO25 and PIPSO25 are not linearly related to sea ice cover and, additionally, each core site reflects specific, local environmental conditions. High IPSO25 and PIPSO25 values may not be directly interpreted as referring to high spring sea ice cover because variable sea ice conditions and enhanced nutrient supply may affect the production of both the sea-ice associated and phytoplankton-derived (open marine, pelagic) biomarker lipids. For a more meaningful interpretation we recommend to carefully consider individually biomarker records to distinguish between cold, sea ice favoring and warm, sea ice diminishing environmental conditions.

Maria-Elena Vorrath et al.

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Maria-Elena Vorrath et al.

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Short summary
We tested the applicability of the organic biomarker IPSO25 for sea ice reconstructions in the industrial era at the Western Antarctic Peninsula. We successfully evaluated our data with satellite sea ice observations. The comparison with marine and ice core records revealed that sea ice interpretations must consider climatic and sea ice dynamics. Sea ice biomarker production is mainly influenced by the Southern Annular Mode, while the El Niño Southern Oscillation seems to have a minor impact.
We tested the applicability of the organic biomarker IPSO25 for sea ice reconstructions in the...
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