New research by scientists from the Netherlands indicates the great North American ice sheets may have caused the transition from a geologically short cycle of about 41,000 years to the longer 100,000 year cycles.
During the ice ages, large ice sheets covered much of North America and Europe. The North American sheets were particularly massive, covering nearly the entire area of modern Canada and even reaching as far south as what are now the states of New York and Pennsylvania.
The researchers applied two scientific models based on the best available data to arrive at ice-age climates, ice volumes and sea levels. The results they uncovered suggest the large North American ice sheets grew so large they began to merge. These super-sheets then expanded further and ultimately--over a period of about 100,000 years--collapsed. This long-term cycle of the world's greatest ice sheets set the new pace for global warming and cooling.
The scientists stress that the data they had to work with was tentative, but they believe this new working model is our best picture yet of the mechanism behind ice age climate cycles.