Terrestrial impact of abrupt changes in the North Atlantic thermohaline circulation: Early Holocene, UK†

  1. Jim D. Marshall*1,
  2. Barbara Lang2,
  3. Stephen F. Crowley3,
  4. Graham P. Weedon4,
  5. Peter van Calsteren5,
  6. Elizabeth H. Fisher6,
  7. Richard Holme6,
  8. Jonathan A. Holmes7,
  9. Richard T. Jones8,
  10. Alan Bedford9,
  11. Steven J. Brooks10,
  12. Jan Bloemendal11,
  13. Kostas Kiriakoulakis12 and
  14. James D. Ball12
  1. 1Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3GP, UK
  2. 2Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, L69 3GP, UK, and Department of Natural Geographical and Applied Sciences, Edge Hill University, Ormskirk L39 4QP, UK
  3. 3Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3GP, UK
  4. 4Climate and Land-Surface Systems Interaction Centre, Department of Geography, University of Wales, Swansea, Singleton Park, Swansea SA2 8PP, UK
  5. 5Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, UK
  6. 6Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3GP, UK
  7. 7Environmental Change Research Centre, Department of Geography, University College, London, 26 Bedford Way, London WC1H 0AP, UK
  8. 8Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter EX4 4RJ, UK
  9. 9Department of Natural Geographical and Applied Sciences, Edge Hill University, Ormskirk L39 4QP, UK
  10. 10Department of Entomology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
  11. 11Department of Geography, University of Liverpool, Liverpool L69 7ZT, UK
  12. 12Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 3GP, UK

    Abstract

    Abrupt cooling events are features of Holocene climate and may recur in the future. We use lake records from Hawes Water, NW England, to quantify the impact of two prominent early Holocene climatic events. Subdecadal oxygen isotope records from sedimentary carbonate (18δOc), dated using thermal ionization mass spectrometry (TIMS) U-series analyses, provide evidence for abrupt cold events, lasting ∼50 and ∼150 yr at 9350 and 8380 yr ago, which correlate with the 9.3 ka and 8.2 ka events recognized in Greenland ice cores. At Hawes Water, mean July air temperatures, inferred from chirono-mid assemblages, decreased by ∼1.6 °C during each event. Calculations show that the isotopic excursions were dominantly caused by decreases in the isotopic composition of meteoric precipitation (18δOp) by ∼1.3‰; this is interpreted as a direct downstream response to cooling and freshening of northeast Atlantic surface water by melting ice sheets. Intermediate in magnitude between events observed in Greenland and central Europe, the effects are consistent with a partial shutdown of the North Atlantic thermohaline circulation.

      • Accepted 26 February 2007.
      • Received 18 December 2006.
      • Revision received 23 February 2007.
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    1. doi: 10.1130/G23498A.1 Geology July 2007 v. 35 no. 7 p. 639-642
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