The study is the first direct evidence the present warmth in the Eastern Canadian Arctic exceeds the peak warmth there in the Early Holocene, when the amount of the Sun's energy reaching the Northern Hemisphere in summer was roughly 9 percent greater than today, researchers said. (Agencies)
The Holocene is a geological epoch that began after Earth's last glacial period ended roughly 11,700 years ago and which continues today.
University of Colorado, Boulder geological sciences Professor Gifford Miller and colleagues used dead moss clumps emerging from receding ice caps on Baffin Island as tiny clocks.
At four different ice caps, radiocarbon dates show the mosses had not been exposed to the elements since at least 44,000 to 51,000 years ago.
"The key piece here is just how unprecedented the warming of Arctic Canada is," said Miller, the study leader.
"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," he said.
Miller and colleagues compiled the age distribution of 145 radiocarbon-dated plants in the highlands of Baffin Island that were exposed by ice recession during the year they were collected by the researchers.
All samples collected were within 1 meter of the ice caps, which are generally receding by 2 to 3 meters a year.
To reconstruct the past climate of Baffin Island beyond the limit of radiocarbon dating, Miller and his team used data from ice cores previously retrieved by international teams from the nearby Greenland Ice Sheet.
The ice cores showed that the youngest time interval from which summer temperatures in the Arctic were plausibly as warm as today is about 120,000 years ago, near the end of the last interglacial period.
"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," said Miller.
The study was published in the journal Geophysical Research Letters.
The study is the first direct evidence the present warmth in the Eastern Canadian Arctic exceeds the peak warmth there in the Early Holocene, when the amount of the Sun's energy reaching the Northern Hemisphere in summer was roughly 9 percent greater than today, researchers said.