October 24, 2013
Arctic Summer Temperatures Warmest They Have Been In 120,000 Years
Lee Rannals for redOrbit.com - Your Universe Online
According to a study published in Geophysical Research Letters, the past 100 years could be the warmest the planet has been in 120,000 years.
University of Colorado Boulder researchers said that average summer temperatures in the Eastern Canadian Arctic during the last 100 years are higher now than during any century in the past 44,000 years, and maybe even as long ago as 120,000 years. The study is the first direct evidence that the present warmth in the Eastern Canadian Arctic exceeds the peak warmth there in the Early Holocene, which was when the sun’s energy in the Northern Hemisphere in the summer was about 9 percent higher than today.
Researchers used dead moss clumps emerging from receding ice caps on Baffin Island as tiny clocks. Radiocarbon dates at four different ice caps showed the mosses had not been exposed to the elements since at least 44,000 to 51,000 years ago. Since radiocarbon dating is only accurate to about 50,000 years and because Earth’s geological record shows it was in a glaciation stage prior to this, it indicates that Canadian Arctic temperatures are at an all-time high for the past 44,000 to 120,000 years.
"The key piece here is just how unprecedented the warming of Arctic Canada is," Gifford Miller, a geological sciences Professor at UC-Boulder and study leader, said in a statement. "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."
The team 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. All the samples were within three feet of the ice caps, which are generally receding by six to nine feet per year.
Many of the ice caps on the 196,000-square-mile Baffin Island rest on relatively flat terrain, usually frozen to their beds. The island is the fifth largest island in the world, and most of it lies above the Arctic Circle.
Miller and colleagues used data from ice cores previously retrieved by international teams from the nearby Greenland Ice Sheet in order to reconstruct the past climate of Baffin Island beyond the limit of radiocarbon dating. The data 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.
"We suggest this is the most likely age of these samples," said Miller. "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. 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."
Temperatures across the Arctic have risen in the past few decades due to climate change. Studies have revealed that temperatures on the ice sheet have climbed seven degrees Fahrenheit since 1991.
A study by Miller and colleagues in 2012 suggested that the trigger for the Little Ice Age was likely a combination of exploding tropical volcanoes and a decrease in solar radiation.
Image Below: University of Colorado Boulder professor Gifford Miller is shown here collecting dead plant samples from the edge of a Baffin Island ice cap. Credit: University of Colorado