A new study led by the University of Colorado at Boulder suggests that the Arctic climate system may be more sensitive to greenhouse warming than first thought.
The international study suggested that the current levels of Earth’s atmospheric carbon dioxide could be high enough to cause significant and irreversible shifts in the various Arctic ecosystems. The conditions on Ellesmere Island in Canada’s High Arctic look to be approaching a point where there could soon be ice free conditions in the Arctic.
“Our findings indicate that CO2 levels of approximately 400 parts per million are sufficient to produce mean annual temperatures in the High Arctic of approximately 0 degrees Celsius (32 degrees F),” said Ashley Ballantyne of the University of Colorado at Boulder. “As temperatures approach 0 degrees Celsius, it becomes exceedingly difficult to maintain permanent sea and glacial ice in the Arctic. Thus current levels of CO2 in the atmosphere of approximately 390 parts per million may be approaching a tipping point for irreversible ice-free conditions in the Arctic.”
The research, to be published in the July issue of the journal Geology, used three independent methods to measure the temperature on Ellesmere Island in the Pliocene Epoch, 2.6 to 5.3 million years ago. They found that the mean annual temperature was 34 degrees Fahrenheit, compared to 32 degrees Fahrenheit today, and that CO2 levels were only slightly higher than today.
“The results of the three independent temperature proxies are remarkably consistent,” said Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado, Museum of Natural History and an associate professor in the geological sciences department and co-author of the study. “We essentially were able to ‘read’ the vegetation in order to estimate air temperatures in the Pliocene.”
“Our findings are somewhat disconcerting regarding the temperatures and greenhouse gas levels during the Pliocene,” said Eberle. “We already are seeing evidence of both mammals and birds moving northward as the climate warms, and I can’t help but wonder if the Arctic is headed toward conditions similar to those that existed during the Pliocene.”
Those conditions consisted of forests of larch, dwarf birch and northern white cedar trees, mosses and herbs, fish, frogs, and mammals including now extinct species like the tiny deer, ancient relatives of the black bear, three-toed horses, small beavers, rabbits, badgers and shrews. Because of the high latitude, the Ellesmere Island site on the Strathcona Fiord was shrouded by darkness six months out of the year, said Natalia Rybczynski of the Canadian Museum of Nature in Ottawa, co-author of the study.
Image Source: Александр