Pleistocene variability of the Subtropical Convergence at East Tasman Plateau - Evidence from planktonic foraminiferal Mg/Ca (ODP Site 1172A).

Nürnberg, Dirk and Groeneveld, Jeroen (2006) Pleistocene variability of the Subtropical Convergence at East Tasman Plateau - Evidence from planktonic foraminiferal Mg/Ca (ODP Site 1172A). Open Access Geochemistry, Geophysics, Geosystems, 7 (4). Q04P11. DOI 10.1029/2005GC000984.

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Abstract

Combined measurements of Mg/Ca and stable oxygen isotopes in tests of the planktonic foraminifer
G. bulloides from Ocean Drilling Program (ODP) Site 1172A (East Tasman Plateau) allowed us to reconstruct
sea surface temperature (SSTMg/Ca), sea surface salinity (SSS), and hence variations in the Subtropical
Convergence (STC) in the southwestern Tasman Sea over the last four major glacial-interglacial changes.
During interglacials the commonly enhanced SSTMg/Ca and SSS correspond to a lowered marine productivity
and a lowered terrigenous flux, implying that the STC separating cool, high-nutrient Subantarctic Surface
Water from warm, saline, oligotrophic Subtropical Surface Water and hence the band of zonal westerlies
responsible for the eolian dust flux were located south of East Tasman Plateau. The warm East Australian
Current was well established during warm periods and propagated far south. During glacial times, SSTMg/Ca
and SSS were lower, while both marine productivity and eolian flux increased. Such conditions prevailed
during glacial Marine Isotope Stages MIS 12, MIS 10, and to a lesser degree MIS 6 and implied the extended
northward influence of Subantarctic SurfaceWater and a shift of the STC to <44�S. The overall climatic signal
at Site 1172A appears to be largely attenuated when compared to published climate records from comparable
latitudes to the west and to the east. SSTMg/Ca amplitudes were more pronounced in the subantarctic Indian
Ocean and at Chatham Rise. They exhibit a consistent pattern suggesting that latitudinal shifts of the STC
occurred synchronously in the subantarctic Indian Ocean and at Chatham Rise but were largely damped at
East Tasman Plateau due to the influence of the East Australian Current.

Document Type: Article
Keywords: Mg/Ca paleothermometry; paleosalinity; planktonic foraminifera; ODP Leg 189
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2005GC000984
ISSN: 1525-2027
Projects: ODP
Date Deposited: 03 Dec 2008 16:51
Last Modified: 31 Jan 2018 10:42
URI: http://oceanrep.geomar.de/id/eprint/1057

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