DECREASING INFLUENCE OF SUB-ANTARCTIC MODE WATER NORTH OF THE TASMAN FRONT OVER THE PAST 150 KYR

A positive relationship between the population size of Globorotalia tr uncatulinoides in deep-sea sediments and thermostad thicknesses in mod e waters of both the northern and the southern hemispheres is document ed. In cores RC12-113, DSDP 588 and DSDP 591 (located north of the Tas man Front) G. truncatulinoides shows a decreasing trend in abundance f rom oxygen isotope stages 6 to 1, suggesting a progressive reduction o f Subantarctic Mode Water (SAMW) thermostads in the northern Tasman Se a. Heating, seasonality and/or a more dynamic Fast Australian Current are suggested as possible mechanisms that cause the piling up of isoth erms that distort thermostads in the northern Tasman Sea. Alternativel y, a more vigorous mixing of the ocean (by convection and overturning) may have been in operation south of the Subtropical Convergence durin g glacial stage 6. Palaeoceanographic conditions during glacial stages 6 and 2 appear to be significantly different. (C) 1997 Elsevier Scien ce B.V.