Thank you.
Abrupt increase in Greenland snow accumulationTHE 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 event. Despite much study of the causes of this event and the mechanisms by which it ended, many questions remain unresolved. Oxygen isotope data from Greenland ice cores suggest that the Younger Dryas ended abruptly, over a period of about 50 years; dust concentrations in these cores show an even more rapid transition (20 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.
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. White, M. Ram,
E. D. Waddington, P. A. Mayewski & G. A. Zielinski
Nature 362, 527 - 529 (08 April 1993)