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Submillenial variations in ocean conditions during deglaciation based on diatom assemblages from the southwest Atlantic

Allen, Claire S., Pike, Jennifer, Pudsey, Carol J. and Leventer, Amy 2005. Submillenial variations in ocean conditions during deglaciation based on diatom assemblages from the southwest Atlantic. Paleoceanography 20 (2) , PA2012. 10.1029/2004PA001055

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Abstract

We present a high-resolution paleoceanographic record of deglaciation based on diatom assemblages from a core located just south of the Polar Front in the southwest Atlantic. Core KC073 is from a sediment drift at the mouth of the Falkland Trough and contains sediments from the Last Glacial Maximum (LGM) to present, dated using radiocarbon dates on bulk organic matter and radiolarian stratigraphy. The site lies along the path of the Antarctic Circumpolar Current (ACC) and immediately downstream of where North Atlantic Deep Water (NADW) is entrained into the ACC. Significant variations in ocean conditions are reflected in high-amplitude changes in diatom concentrations and assemblage composition. The diatom assemblage at the LGM indicates that winter sea ice extent was at least 5° farther north than present until at least 19.0 ka (calendar years) and summer sea ice may have occasionally extended over the site, but for the most part it lay to the south. During deglaciation, Chaetoceros resting spores (CRS) dominate the diatom assemblage with valve concentrations in excess of 500 × 106 valves per gram. Submillennial-scale variations in the numbers of CRS and Thalassiosira antarctica occur throughout the late deglacial and dominate the changes in diatom concentration. We propose that the influx of CRS is controlled by the flow of NADW over the Falkland Plateau. As such our data provide unique evidence that NADW impacted on this sector of the Southern Ocean during deglaciation. During the Holocene the sedimentation rate dramatically reduced. We suggest that the ACC flow increased over the site and inhibited settling and winnowed the surface sediments.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QE Geology
Uncontrolled Keywords: Southern Ocean; late Quaternary; paleoceanography; sedimentology; diatom
Additional Information: Publisher's copyright requirements "Permission to Deposit an Article in an Institutional Repository. Adopted by Council 13 December 2009. AGU allows authors to deposit their journal articles if the version is the final published citable version of record, the AGU copyright statement is clearly visible on the posting, and the posting is made 6 months after official publication by the AGU." See http://www.agu.org/pubs/authors/usage_permissions.shtml
Publisher: American Geophysical Union
ISSN: 0883-8305
Last Modified: 04 Jun 2017 01:39
URI: http://orca.cf.ac.uk/id/eprint/1297

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