CHANGES IN THE STRENGTH OF THE ICELAND-SCOTLAND OVERFLOW WATER IN THELAST 200,000 YEARS - EVIDENCE FROM MAGNETIC-ANISOTROPY ANALYSIS OF CORE SU90-33

Results from a high resolution study of magnetic anisotropy combined w ith mineral magnetic analysis, clay analysis and oxygen isotopes strat igraphy are reported for core SU90-33 located (60 degrees 34'4N, 22 de grees 05'1W) at 2400 m water depth along the Iceland-Scotland overflow water (ISOW), a branch of the North Atlantic Deep Water (NADW). This core covers the last 6 climatic stages. The main magnetic mineral is l ow Ti-content magnetite with Very slight changes in the grain size. Th e susceptibility record, corrected for the carbonate content, indicate s down-core Variations in the amount of magnetite which largely co-var y with the changes in the proportion of smectite in the clay fraction. Both parameters are climatically controlled, with lower values during glacial than during interglacial periods. The measurements of the ani sotropy of magnetic susceptibility document down-core changes in the d egree of anisotropy, with significantly higher Values during interglac ial periods than during glacial times. These changes appear to be rela ted to differences in the degree of alignment of the magnetic particle s and not to changes in grain shape, providing evidence that they aris e from changes in strength of the bottom water circulation. Therefore, the strength of the contour current associated to the transport of th e ISOW appears to have been significantly larger during climatic stage s 5, 3 and 1 than during stages 6, 4 and 2. (C) 1997 Elsevier Science B.V.