Oct 24, 2013 04:16 PM EDT
The average summer over the last century in the Eastern Canadian Arctic has exceeded the same such average in any previous over the last 44,000 years, according to a University of Colorado at Boulder press release.
Lead author Gifford Miller and his colleagues conducted the first study, published Monday in the journal Geophysical Research Letters, with direct evidence that the present warmth in the Eastern Canadian Arctic exceeds a previous high.
In a period known as the Early Holocene, the sun's energy reaching the Northern Hemisphere was during the summer was about nine percent stronger than it is today. The Holocene is a period some 12,000 years ago when a geological epoch began after the last glacial period ended.
"The key piece here is just how unprecedented the warming of Arctic Canada is," said Miller, also a fellow at CU-Boulder's Institute of Arctic and Alpine Research. "This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere."
For their study, the researchers examined dead moss clumps found in receding ice caps. Acting as clocks, radiocarbon dating of the moss shows they had not seen the sun anytime in the last 44,000 to 51,000 years. Miller said radiocarbon dating can only be accurate up to 50,000 years, so he believes the region is experience its hottest temperatures in nearly 120,000 years.
"We suggest this is the most likely age of these samples," said Miller.
Based on ice cores examined by the researchers, the youngest interval of time in which temperatures were as high as they are now was at least 120,000 years ago.
"Although the Arctic has been warming since about 1900, the most significant warming in the Baffin Island region didn't really start until the 1970s," said Miller. "And it is really in the past 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to eventually disappear, even if there is no additional warming."
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