September 8, 2010
A week ago, Nature News reported on several recent studies that cast doubt on a comet as the cause of the Younger Dryas Ice Age, which took place 13,000 years ago. Now, a study posted in the journal Nature has found that the period may have actually been one of warming and thawing of glaciers in the Southern Hemisphere. While the change in ocean temperatures at the time did block the Gulf Stream, preventing warm water from reaching the colder north, it seems that other climate altering currents, known collectively as the conveyor belt, were also stopped from bringing enough deep, cold water to the south, resulting in a thaw.
An international team led by paleoclimatologist Michael Kaplan of the Lamont-Doherty Earth Observatory in Palisades, New York, studied a part of New Zealand called Irishman Stream, an area littered with soil deposits and boulders displaced by glaciers during the ice age, to see what effects the Younger Dryas period had on the area. By doing chemical analysis on the rocks in the area, the team found that the rocks were deposited as the glaciers were retreating. Further analysis of the isotope beryllium-10 found that the rocks were first exposed to open air between 11,100 and 13,700 years ago, meaning these glaciers were melting away well within the Younger Dryas period that sent much of the Northern Hemisphere into a near-glacial freeze.
The study will run in tomorrow’s issue of Nature. For more, see the report from ScienceNOW.