Paleoceanography and ice sheet variability offshore Wilkes Land, Antarctica - Part 1: Insights from late Oligocene astronomically paced contourite sedimentation

Autor: Salabarnada, Ariadna, Escutia, Carlota, Röhl, Ursula, Nelson, C. Hans, McKay, Robert, Jiménez-Espejo, Francisco J., Bijl, Peter K., Hartman, Julian D., Strother, Stephanie L., Salzmann, Ulrich, Evangelinos, Dimitris, López-Quirós, Adrián, Flores, José Abel, Sangiorgi, Francesca, Ikehara, Minoru, Brinkhuis, Henk, Marine palynology and palaeoceanography, Marine Palynology
Přispěvatelé: Ministerio de Economía y Competitividad (España), European Commission, Natural Environment Research Council (UK), Marine palynology and palaeoceanography, Marine Palynology
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Climate of the Past, 14(7), 991. European Geosciences Union
Digital.CSIC. Repositorio Institucional del CSIC
instname
Climate of the Past, Vol 14, Pp 991-1014 (2018)
ISSN: 1814-9324
1814-9332
Popis: Antarctic ice sheet and Southern Ocean paleoceanographic configurations during the late Oligocene are not well resolved. They are however important to understand the influence of high-latitude Southern Hemisphere feedbacks on global climate under CO scenarios (between 400 and 750 ppm) projected by the IPCC for this century, assuming unabated CO emissions. Sediments recovered by the Integrated Ocean Drilling Program (IODP) at Site U1356, offshore of the Wilkes Land margin in East Antarctica, provide an opportunity to study ice sheet and paleoceanographic configurations during the late Oligocene (26-25 Ma). Our study, based on a combination of sediment facies analysis, magnetic susceptibility, density, and X-ray fluorescence geochemical data, shows that glacial and interglacial sediments are continuously reworked by bottom currents, with maximum velocities occurring during the interglacial periods. Glacial sediments record poorly ventilated, low-oxygenation bottom water conditions, interpreted as resulting from a northward shift of westerly winds and surface oceanic fronts. Interglacial sediments record more oxygenated and ventilated bottom water conditions and strong current velocities, which suggests enhanced mixing of the water masses as a result of a southward shift of the polar front. Intervals with preserved carbonated nannofossils within some of the interglacial facies are interpreted as forming under warmer paleoclimatic conditions when less corrosive warmer northern component water (e.g., North Atlantic sourced deep water) had a greater influence on the site. Spectral analysis on the late Oligocene sediment interval shows that the glacial-interglacial cyclicity and related displacements of the Southern Ocean frontal systems between 26 and 25Ma were forced mainly by obliquity. The paucity of iceberg-rafted debris (IRD) throughout the studied interval contrasts with earlier Oligocene and post-Miocene Climate Optimum sections from Site U1356 and with late Oligocene strata from the Ross Sea, which contain IRD and evidence for coastal glaciers and sea ice. These observations, supported by elevated sea surface paleotemperatures, the absence of sea ice, and reconstructions of fossil pollen between 26 and 25 Ma at Site U1356, suggest that open-ocean water conditions prevailed. Combined, this evidence suggests that glaciers or ice caps likely occupied the topographic highs and lowlands of the now marine Wilkes Subglacial Basin (WSB). Unlike today, the continental shelf was not overdeepened and thus ice sheets in the WSB were likely land-based, and marine-based ice sheet expansion was likely limited to coastal regions.
This research used samples and data provided by the Integrated Ocean Drilling Program, now the International Ocean Discovery Program (IODP). We thank thestaff onboard IODP Exp. 318 and at the Gulf Coast, the Bremen, and the Kochi IODP core repositories for assistance in core handling and shipping. We thank Vera Lukies (MARUM) for technical support with XRF core scanning and Shizu Yanagimoto (KOCHI) fortechnical supportwith CT scans.We alsothank theconstructive comments of an anonymous reviewer and Steven Pekar that have helped to improve this paper. Funding for this research is provided by the Spanish Ministerio de Economía y Competitividad (grants CTM 2011-24079 and CTM2014-60451-C2-1-P), co-funded by the European Union through FEDER funds. Ulrich Salzmann thanks the Deutsche Forschungsgemeinschaft (DFG) (RO 1113/6). Peter K. Bijl, Francesca Sangiorgi, and Julian D. Hartman acknowledge funding through the NWO polar programme grant no 866.10.110. Peter K. Bijl acknowledges funding through NWO-VENI grant no 863.13.002. Ulrich Salzmann acknowledges funding received from the Natural Environment Research Council (NERC grant NE/H000984/1).
Databáze: OpenAIRE
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