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Letters to Nature

Nature 362, 527-529 (8 April 1993) | doi:10.1038/362527a0; Received 18 September 1992; Accepted 2 March 1993

Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event

R. B. Alley*, D. A. Meese†, C. A. Shuman*, A. J. Gow†, K. C. Taylor‡, P. M. Grootes§, J. W. C. Whiteparallel, M. Ram, E. D. Waddington£, P. A. Mayewski** & G. A. Zielinski**

  1. *Earth System Science Center and Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
  2. †Snow and Ice Branch, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755, USA
  3. ‡Desert Research Institute, University of Nevada System, Reno, Nevada 89506, USA
  4. §Quaternary Isotope Laboratory, University of Washington, Seattle, Washington 98195, USA
  5. parallelInstitute for Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309, USA
  6. Department of Physics, University at Buffalo, Amherst, New York 14260, USA
  7. £Geophysics Program, University of Washington, Seattle, Washington 98195, USA
  8. **Glacier Research Group, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, New Hampshire 03824, USA
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THE warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate, the best-known of which is the Younger Dryas event1. Despite much study of the causes of this event and the mechanisms by which it ended, many questions remain unresolved1. Oxygen isotope data from Greenland ice cores2–4 suggest that the Younger Dryas ended abruptly, over a period of about 50 years; dust concentrations2,4 in these cores show an even more rapid transition (less than or similar to20 years). This extremely short timescale places severe constraints on the mechanisms underlying the transition. But dust concentrations can reflect subtle changes in atmospheric circulation, which need not be associated with a large change in climate. Here we present results from a new Greenland ice core (GISP2) showing that snow accumulation doubled rapidly from the Younger Dryas event to the subsequent Preboreal interval, possibly in one to three years. We also find that the accumulation-rate change from the Oldest Dryas to the Bø11ing/Allerød warm period was large and abrupt. The extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the North Atlantic climate system.