Palaeoclimate and Ice-Sheet Dynamics in the Southern Ocean

Gerhard.Kuhn [ at ]


For a better understanding of future climate it is inevitably to study earth history and past climate changes. The objective of this thesis was to analyse seasonal-to-millennial-scale fluctuations during the last glacial and deglacial period. Therefore, core sites located in the Atlantic Sector of the Southern Ocean providing high sedimentation rates, of up to a few metres per thousand years were investigated. Varved sediments originating from channel-ridge systems in the southeastern Weddell Sea were analysed, including thin section and X-radiographs production, X-ray fluorescence-scanning, RADIUS particle analyses, and of course varve counting. The investigations reveal highly dynamic sedimentation in the channel-ridge systems, reflecting seasonal changes of the thermohaline current during the LGM possibly related to changes in katabatic winds and hence coastal polynya activity. Spectral analysis detected decadal-to-centennial-scale oscillations in varve thicknesses strongly correlating with the periods of solar cycles, therefore suggesting that solar cycles modulated sedimentation in the core site area during the LGM. Sedimentation in the southeastern Weddell Sea possibly also indicates multiple fluctuations of East Antarctic Ice Sheet during the LGM. The magnetic susceptibility record of Scotia Sea cores show a one-to-one coupling with the non-sea-salt Ca2+ flux of East Antarctic EDML ice core, a confident atmospheric dust proxy. This clearly identifies atmospheric circulation as supplier of the magnetic susceptibility signal in the Scotia Sea, and enables the establishment of a high-resolution age model. Patagonia can be identified as major dust source during the LGM. Biogenic opal was determined by leaching, as well as estimated using colour b*, wet-bulk density, Si/Ti count ratios, and Fourier transform infrared spectroscopy (FTIRS). All methods can be used to detect general biogenic opal trends, thus FTIRS provides the most reliable estimation. The biogenic opal flux curve of MD07-3134 is one of the first continuous palaeoproductivity records over the last 92.5 ka for the Southern Ocean. It exhibits a relatively complicated glacial-tointerglacial pattern with large-amplitude, millennial-scale fluctuations in bioproductivity. published within papers: Sprenk, D., Weber, E. M., Kuhn, G., Rosén, P., Frank, M., Molina-Kescher, M., Liebetrau, V., Röhling, H. G. (2013): Southern Ocean bioproductivity during the last glacial cycle - New detection method and decadal-scale insight from the Scotia Sea. Geological Society Special Publication, 245-261, doi: 10.1144/SP381.17. Sprenk, D., Weber, M. E., Kuhn, G., Wennrich, V., Hartmann, T., Seelos, K., 2014. Seasonal changes in glacial polynya activity inferred from Weddell Sea varves. Clim. Past 10, 1239-1251, doi: 10.5194/cp-10-1239-2014

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Thesis (PhD)
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Sprenk, D. (2013): Palaeoclimate and Ice-Sheet Dynamics in the Southern Ocean , PhD thesis, Universität zu Köln.

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Geographical region

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ANT > VI > 3
ANT > VIII > 5

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