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Volume 14, issue 9 | Copyright
Clim. Past, 14, 1275-1297, 2018
https://doi.org/10.5194/cp-14-1275-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 04 Sep 2018

Research article | 04 Sep 2018

Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica – Part 3: Insights from Oligocene–Miocene TEX86-based sea surface temperature reconstructions

Julian D. Hartman1, Francesca Sangiorgi1, Ariadna Salabarnada2, Francien Peterse1, Alexander J. P. Houben3, Stefan Schouten4, Henk Brinkhuis1,4, Carlota Escutia2, and Peter K. Bijl1 Julian D. Hartman et al.
  • 1Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584CB Utrecht, the Netherlands
  • 2Instituto Andaluz de Ciencias de la Tierra, CSIC/Universidad de Granada, Avenida de las Palmeras 4, 18100 Armilla, Granada, Spain
  • 3Applied Geosciences Team, Netherlands Organisation for Applied Scientific Research (TNO), Princetonlaan 6, 3584CB Utrecht, the Netherlands
  • 4NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University, Landsdiep 4, 1797SZ 't Horntje, Texel, the Netherlands

Abstract. The volume of the Antarctic continental ice sheet(s) varied substantially during the Oligocene and Miocene ( ∼ 34–5Ma) from smaller to substantially larger than today, both on million-year and on orbital timescales. However, reproduction through physical modeling of a dynamic response of the ice sheets to climate forcing remains problematic, suggesting the existence of complex feedback mechanisms between the cryosphere, ocean, and atmosphere systems. There is therefore an urgent need to improve the models for better predictions of these systems, including resulting potential future sea level change. To assess the interactions between the cryosphere, ocean, and atmosphere, knowledge of ancient sea surface conditions close to the Antarctic margin is essential. Here, we present a new TEX86-based sea surface water paleotemperature record measured on Oligocene sediments from Integrated Ocean Drilling Program (IODP) Site U1356, offshore Wilkes Land, East Antarctica. The new data are presented along with previously published Miocene temperatures from the same site. Together the data cover the interval between  ∼ 34 and  ∼ 11Ma and encompasses two hiatuses. This record allows us to accurately reconstruct the magnitude of sea surface temperature (SST) variability and trends on both million-year and glacial–interglacial timescales. On average, TEX86 values indicate SSTs ranging between 10 and 21°C during the Oligocene and Miocene, which is on the upper end of the few existing reconstructions from other high-latitude Southern Ocean sites. SST maxima occur around 30.5, 25, and 17Ma. Our record suggests generally warm to temperate ocean offshore Wilkes Land. Based on lithological alternations detected in the sedimentary record, which are assigned to glacial–interglacial deposits, a SST variability of 1.5–3.1°C at glacial–interglacial timescales can be established. This variability is slightly larger than that of deep-sea temperatures recorded in MgCa data. Our reconstructed Oligocene temperature variability has implications for Oligocene ice volume estimates based on benthic δ18O records. If the long-term and orbital-scale SST variability at Site U1356 mirrors that of the nearby region of deep-water formation, we argue that a substantial portion of the variability and trends contained in long-term δ18O records can be explained by variability in Southern high-latitude temperature and that the Antarctic ice volume may have been less dynamic than previously thought. Importantly, our temperature record suggests that Oligocene–Miocene Antarctic ice sheets were generally of smaller size compared to today.

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We reconstructed sea surface temperatures for the Oligocene and Miocene periods (34–11 Ma) based on archaeal lipids from a site close to the Wilkes Land coast, Antarctica. Our record suggests generally warm to temperate surface waters: on average 17 °C. Based on the lithology, glacial and interglacial temperatures could be distinguished, showing an average 3 °C offset. The long-term temperature trend resembles the benthic δ18O stack, which may have implications for ice volume reconstructions.
We reconstructed sea surface temperatures for the Oligocene and Miocene periods (34–11 Ma) based...
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