Rapid climatic variations during marine isotopic stage 3: magnetic analysis of sediments from Nordic Seas and North Atlantic

The bulk magnetic parameters of seven deep-sea cores distributed from the Nordic Seas (67N degrees) to the North Atlantic as far south as the Bermuda Rise (33 degrees N) exhibit short-term variations which correlate with rapid climatic changes during marine isotopic stage 3 (MIS3). The magnetic mineralogy is uniformly dominated by well sorted low Ti-content magnetites indicating that these variations are due to variations in the relative amount of magnetic minerals. Because the magnetic minerals predominantly originate from one common source area (the Nordic basaltic province), these changes arise from changes in the efficiency of the transport of the magnetic particles by deep currents from the source to the site of deposition. These results therefore show that the fast climatic changes are related to coeval fast changes in the strength of the deep-sea circulation. The latter was active/reduced during the interstadials/stadials and Heinrich events transporting the magnetic particles from the Norwegian Sea into the North Atlantic ocean along a path similar to the present path of the NADW. It is tentatively suggested that the Faeroe-Shetland Channel and the Denmark Strait were the only two active paths for the overflow water during M1S3. The presence of magnetic oscillations in the Bermuda Rise core in phase with those from the North Atlantic indicates that the activity of the southern Newfoundland Basin gyre was linked to that of the NADW during MISS. (C) 1999 Elsevier Science B.V. All rights reserved.