Source, timing, frequency and flux of ice-rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis

Authors


  • Anna I. Haapaniemi (e-mail: anna.haapaniemi@helsinki.fi), Department of Geology, P.O. Box 64, FIN-00014, University of Helsinki, Helsinki, Finland; James D. Scourse (e-mail: j.scourse@bangor.ac.uk), Hilary Kennedy and Paul Kennedy, School of Ocean Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK; Victoria L. Peck, British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Sidney R. Hemming, Department of Earth and Environmental Sciences, Lamont–Doherty Earth Observatory, 61 Route 9W Palisades, NY 10964, USA; Mark F.A. Furze, Earth & Planetary Sciences Section, Department of Physical Science, Grant MacEwan University, P.O. Box 1796, Edmonton, Alberta, T5J 2P2, Canada; Anna J. Pieńkowski, Department of Earth and Atmospheric Sciences, 1-26 Earth Science Building, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada; William E.N. Austin, John Walden and Emilie Wadsworth, School of Geography and Geosciences, University of St Andrews, Irvine Building, North Street, St Andrews KY16 9AL,UK; Ian R. Hall, School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK

Abstract

Haapaniemi, A.I., Scourse, J.D., Peck, V.L., Kennedy, H., Kennedy, P., Hemming, S.R., Furze, M.F.A., Pieńkowski, A.J., Austin, W.E.N., Walden, J., Wadsworth, E. & Hall, I.R. 2010: Source, timing, frequency and flux of ice-rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis. Boreas, Vol. 39, pp. 576–591. 10.1111/j.1502-3885.2010.00141.x. ISSN 0300-9483.

Increased fluxes of ice-rafted detritus (IRD) from European ice sheets have been documented some 1000–1500 years before the arrival of Laurentide Ice Sheet (LIS)-sourced IRD during Heinrich (H) events. These early fluxes have become known as ‘precursor events’, and it has been suggested that they have mechanistic significance in the propagation of H events. Here we present a re-analysis of one of the main cores used to generate the precursor concept, OMEX-2K from the Goban Spur covering the last 30 ka, in order to identify whether the British–Irish Ice Sheet (BIIS) IRD fluxes occur only as precursors before H layers. IRD characterization and planktonic foraminiferal δ18O measurements constrained by a new age model have enabled the generation of a continuous record of IRD sources, timing, frequency and flux, and of local contemporary hydrographic conditions. The evidence indicates that BIIS IRD precursors are not uniquely, or mechanistically, linked to H events, but are part of the pervasive millennial-scale cyclicity. Our results support an LIS source for the IRD comprising H layers, but the ambient glacial sections are dominated by assemblages typical of the Irish Sea Ice Stream. Light isotope excursions associated with H events are interpreted as resulting from the melting of the BIIS, with ice-sheet destabilization attributed to eustatic jumps generated by LIS discharge during H events. This positive-feedback mechanism probably caused similar responses in all circum-Atlantic ice-sheet margins, and the resulting gross freshwater flux contributed to the perturbation of the Atlantic Meridional Overturning Circulation during H events.

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