Shifts in oceanic and atmospheric boundaries in the Tasman Sea (Southwest Pacific) during the Late Pleistocene: evidence from organic carbon and lithogenic fluxes

The fluctuation in primary production and mineral dust accumulation was estimated to better understand marine and terrestrial environments in the Tasman Sea, southwest Pacific, during the Late Pleistocene. Maxima in primary production were observed during late Oxygen Isotope Stage (OIS) 2, middle OIS 4 and late OIS 6 for core NGC 97 while minimum values were observed in OIS 5. On the other hand, primary production was low and relatively uniform in cores NGC 100 and 99 during the last 180 kyr. These results suggest that the Tasman Front existed between NGC 99 (similar to30degreesS) and NGC 97 (similar to35degreesS) during the last 180 kyr and migrated northward by a few degree (similar to2-3degrees latitude) in OIS 2 and 4. The mass accumulation rates (MARs) of mineral aerosol (MAR(aerosol)) estimated from the Al concentration increased southward during each OIS (excluding OIS 2 in cores NGC 100 and 99). The MAR(aerosol) was more enhanced during glacials than interglacials in cores NGC 100 and 97 while NGC 99 showed no definite fluctuation. These results suggest small northward shifts (similar to2-3degrees latitude) of the high pressure subtropical ridge, dividing the tropical easterly circulation from the mid-latitude westerlies, took place during glacial times. These results demonstrate that the boundary between subtropical and temperate features in both ocean and atmosphere consistently migrated by a few degrees between glacials and interglacials. In addition, profiles of MAR of organic carbon, biogenic opal and primary productivity were quite similar for cores NGC 97 and S2612 (32degrees19.84'N, 157degrees51.00'E), which shows that the boreal and austral transition zones between subtropical and subarctic waters migrated almost synchronously along the latitudinal transect around 160degreesE during the last 150 kyr [Kawahata et al., J. Oceanogr. 55 (1999) 521-532]. Therefore boreal and austral mid-latitudes could have probably experienced similar fluctuations in the oceanic and atmospheric environments. (C) 2002 Elsevier Science B.V. All rights reserved.