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

The history of coastal surface currents in the eastern Indian Ocean over the last similar to 130 kyr has been studied through the application of the FI-2 transfer function to planktic foraminifera in deep-sea cores in a N-S transect offshore Western Australia. The concept of sea-surface temperature (SST) gradient residuals is the amount by which the sea-surface temperature gradient of a given time differs from that in the modern sea. The SST gradient residuals for several episodes of climate extremes in the Late Quaternary [the last glacial maximum (similar 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 130 kyr B.P.)] indicate that areas north of similar to 18 degrees S off Western Australia have changed very little during the extremes in climate over the last similar to 130 kyr, while south of similar to 18 degrees S there have been significant changes in surface-water temperatures. Large areas of anomalously cool surface-water were established off North West Cape (22 degrees S-24 degrees S) during both glacial and interglacial extremes. These reflect the increased influence of the West Australian current on the surface-water circulation. During the last glacial maximum and at the end of the penultimate glaciation, cold sea-surface temperature anomalies were established near to the coast, indicating 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 degrees-25 degrees S, where a zone of cold water was maintained.