LARGE-SCALE REORGANIZATION OF OCEAN CURRENTS OFFSHORE WESTERN-AUSTRALIA DURING THE LATE QUATERNARY

The history of coastal surface currents in the eastern Indian Ocean ov er the last similar to 130 kyr has been studied through the applicatio n of the FI-2 transfer function to planktic foraminifera in deep-sea c ores in a N-S transect offshore Western Australia. The concept of sea- surface temperature (SST) gradient residuals is the amount by which th e sea-surface temperature gradient of a given time differs from that i n the modern sea. The SST gradient residuals for several episodes of c limate extremes in the Late Quaternary [the last glacial maximum (simi lar to 20 kyr B.P.), the last interglacial maximum (similar to 122-120 kyr B.P.), and at the end of the penultimate glaciation (similar to 1 30 kyr B.P.)] indicate that areas north of similar to 18 degrees S off Western Australia have changed very little during the extremes in cli mate over the last similar to 130 kyr, while south of similar to 18 de grees S there have been significant changes in surface-water temperatu res. Large areas of anomalously cool surface-water were established of f North West Cape (22 degrees S-24 degrees S) during both glacial and interglacial extremes. These reflect the increased influence of the We st Australian current on the surface-water circulation. During the las t glacial maximum and at the end of the penultimate glaciation, cold s ea-surface temperature anomalies were established near to the coast, i ndicating that the Leeuwin Current did not warm the coastal zone as it does today. During the last interglacial maximum the Leeuwin Current flowed as an intensified current in a narrow zone close to the coast, but did not significantly warm surface-waters offshore as far as 20 de grees-25 degrees S, where a zone of cold water was maintained.