IS THE YOUNGER DRYAS GLOBAL IN EXTENT?

Evidence for the Younger Dryas cooling event (~10,500 - 13,000 calendar years ago) is found in a variety of climatic proxies, such as variations in pollen records, composition of ice cores, grain size in loess deposits, chemistry of ocean sediments, and the presence of glacial moraines. Here, we evaluate worldwide evidence, chronological control and duration of the Younger Dryas and compare these results to climate models. The Younger Dryas is well established in the North Atlantic region becoming more problematic in both evidence and chronological control in other areas of the world. In addition, ocean records reveal conflicting evidence for Younger Dryas forcing mechanisms and the timing of events. Further the Younger Dryas may be mistaken for other short term cold intervals such as the 8.2 ka event, when dating control is weak. Nevertheless, the Younger Dryas appears to be global in scale, albeit the signals vary in strength. We compare the proxy records to the ocean general circulation model coupled to the energy and moisture balance atmospheric model. We find the model results compare favourably with the temperature change interrupted from palaeoclimatic reconstruction and the general duration of the cooling of the Younger Dryas.