Frontal movement of the subtropical convergence south of Tasmania over the last 60,000 years
Abstract
The northern boundary of the Southern Ocean is the subtropical convergence (STC), which sits just to the south of Tasmania today. Alkenone temperature data was used to reconstruct paleo-ocean circulation and frontal movement of the STC over the last 60 Kyrs on the South Tasman Rise (STR). Alkeonone data was collected from four gravity cores that provide a latitudinal transect across the STR and a longitudinal perspective at the north of the Rise with the eastern core location tracking possible influence from warm waters of the East Australian Current (EAC). Frontal movement can be determined by changes in the temperature gradient between the cores through time. Frontal movement can be determined by changes in the temperature gradient between the cores through time. The STC front moved numerous times across the STR area during the last 60 kyrs as reflected by temperature fluctuation across the latitudinal transect. The STC was at its most southerly position , south of 46S, between MIS stage 3 and early in the last glaciation (40 to 20 ka). After that time (20 to 13 ka) it moved to a more northerly position in the late glacial and early deglacial period , to between 45 and 46S. In the early deglaciation,(12 to 11.5 ka) the STC was located more northerly still (around 45S) and to the east cold temperatures indicate diminished EAC influences and/or that the front sat north of 44S. In the latest deglaciation (11.5 to 10 ka), the STC was located was in a similar position over the STR but to the east the EAC influence was strong or the STC sat south of 44S. In the early Holocene, (10-7ka), the STC was located further south , between 46 and 45 S but to the east moved north of 44S . In the late Holocene, (7-0ka), the STC retreated south of 46 S but remained more northerly to the east of the STR . During MIS stages 3 and 4 (45 and 60 ka) the STC sat as far north as in the early deglaciation. These reconstructions suggest that Southern Ocean conditions to the south of Tasmania were most extreme in late stage in the early glaciation and was in a similar location in the mid to late Holocene.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMPP13B1286M
- Keywords:
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- 4936 Interglacial;
- 4954 Sea surface temperature