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Tuesday, February 17, 2009

Jostein Bakke et al., Nature Geoscience, Rapid oceanic and atmospheric changes during the Younger Dryas cold period

Nature Geoscience, published online 15 February 2009 | doi:10.1038/ngeo439

Rapid oceanic and atmospheric changes during the Younger Dryas cold period

Jostein Bakke*,1,2, Øyvind Lie2, Einar Heegaard2,3, Trond Dokken2, Gerald H. Haug4,5, Hilary H. Birks2,3, Peter Dulski6 and Trygve Nilsen7

Letter abstract

The Younger Dryas event, which began approximately 12,900 years ago, was a period of rapid cooling in the Northern Hemisphere, driven by large-scale reorganizations of patterns of atmospheric and oceanic circulation1, 2, 3. Environmental changes during this period have been documented by both proxy-based reconstructions3 and model simulations4, but there is currently no consensus on the exact mechanisms of onset, stabilization or termination of the Younger Dryas5, 6, 7, 8. Here we present high-resolution records from two sediment cores obtained from Lake Kråkenes in western Norway and the Nordic seas. Multiple proxies from Lake Kråkenes are indicative of rapid alternations between glacial growth and melting during the later Younger Dryas. Meanwhile, reconstructed sea surface temperature and salinity from the Nordic seas show an alternation between sea-ice cover and the influx of warm, salty North Atlantic waters. We suggest that the influx of warm water enabled the westerly wind systems to drift northward, closer to their present-day positions. The winds thus brought relatively warm maritime air to Northern Europe, resulting in rising temperatures and the melting of glaciers. Subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice, which forced the westerly winds back to the south, cooling Northern Europe. We conclude that rapid alternations between these two states immediately preceded the termination of the Younger Dryas and the permanent transition to an interglacial state.

  1. Department of Geography, University of Bergen, Fosswinckelsgt 6, N-5020 Bergen, Norway
  2. Bjerknes Centre for Climate Research, Allégaten 55, N-5007 Bergen, Norway
  3. Department of Biology, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
  4. Geological Institute, Department of Earth Sciences, ETH Zürich, CH-8092 Zürich, Switzerland
  5. DFG Leibniz Center for Earth Surface Process and Climate Studies, Institute for Geosciences, Potsdam University, Potsdam D-14476, Germany
  6. Section 3.3., GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany
  7. Department of Mathematics, University of Bergen, Johannes Brunsgate 12, N-5008 Bergen, Norway

*Corresponding author, e-mail:

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