A Different Kind of Global Warming; UMaine Researcher Looks at how the World Emerged from the Last Ice Age
Contact: David Munson (207) 581-3777
A new study of glacial retreat shows that much of the world emerged from the last ice age simultaneously, according to two leading climate change scientists at Columbia University and at the University of Maine. The exceptions were areas of the North Atlantic, which remained in a deep freeze 2,500 years longer.
The end of the recurring, 100,000-year glacial cycles is one of the most prominent and readily identifiable features in records of the Earth’s recent climate history. Yet one of the most puzzling questions in climate science has been why different parts of the world, most notably Greenland, appear to have warmed at different times and at different rates after the end of the last Ice Age.
The new study, reported recently in the journal Science, suggests that most of the Earth did, in fact, begin warming at the same time roughly 17,500 years ago. In addition, scientists suggest that ice core records from Greenland, which show that average temperatures there did not warm appreciably until about 15,000 years ago, may have remained in a hyper-cold state largely as a result of events triggered by warming elsewhere.
The research, led by Joerg Schaefer from the Lamont-Doherty Earth Observatory, a member of the Earth Institute at Columbia University, and George Denton at the University of Maine, relied on a method known as cosmogonic or surface-exposure dating, which enabled the scientists to determine how long rock surfaces have been exposed since the glaciers retreated.
As cosmic rays penetrating the Earth’s atmosphere strike the scoured rock, they form an isotope of the element beryllium at a known rate. By measuring the minute amounts of beryllium in rock samples from glacial moraines in California and New Zealand and comparing these data to previously published results from Wyoming, Oregon, Montana Argentina, Australia and Switzerland, the scientists were able to narrow down when glaciers around the world began to retreat. Additional studies from tropical South America southern Tibet also produced similar results.