Changes in the strength of the Iceland-Scotland Overflow Water in the last 200,000 years: Evidence from magnetic anisotropy analysis of core SU90-33

• Published in: Earth and Planetary Science Letters
• Main Authors: Kissel, C., Laj, C., Lehman, B., Labyrie, L., Bout‑Roumazeilles, Viviane
• Other Authors: Centre des Faibles Radioactivités, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1997
• Subjects: anisotropy; magnetite; smectite; paleoclimatology; North Atlantic Deep Water; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Iceland; NADW; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-03281707; https://hal.archives-ouvertes.fr/hal-03281707/document; https://hal.archives-ouvertes.fr/hal-03281707/file/Changes%20in%20the%20strength%20of%20the%20Iceland%E2%80%93Scotland%20Overflow%20Water%20in%20the%20last%20200-V1.pdf; https://doi.org/10.1016/S0012-821X(97)00146-5

International audience Results from a high resolution study of magnetic anisotropy combined with mineral magnetic analysis, clay analysis and oxygen isotopes stratigraphy are reported for core SU90-33 located (60°34'4N, 22°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 low Ti-content magnetite with very slight changes in the grain size. The susceptibility record, corrected for the carbonate content, indicates down-core variations in the amount of magnetite which largely co-vary 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 anisotropy of magnetic susceptibility document down-core changes in the degree of anisotropy, with significantly higher values during interglacial periods than during glacial times. These changes appear to be related to differences in the degree of alignment of the magnetic particles and not to changes in grain shape, providing evidence that they arise from changes in strength of the bottom water circulation. Therefore, the strength of the contour current associated to the transport of the ISOW appears to have been significantly larger during climatic stages 5, 3 and 1 than during stages 6, 4 and 2.