Arctic temperatures have risen by about 1.8 degrees F, or 1 degree C, in the past two decades in response to anthropogenic greenhouse warming, a trend expected to continue in the coming decades and centuries, said Ballantyne. Greenhouse gases in the atmosphere have risen from about 280 parts per million during the pre-industrial era on Earth to about 390 parts per million today.
During the Pliocene, Ellesmere Island hosted forests of larch, dwarf birch and northern white cedar trees, as well as mosses and herbs, including cinquefoils. The island also was home to fish, frogs and now extinct mammals that included 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 Rybczynski.
Fossils are often preserved in a process known as permineralization, in which mineral deposits form internal casts of organisms. But at the Ellesmere Island site known as the "Beaver Pond site," organic materials -- including trees, plants and mosses -- have been "mummified" in peat deposits, allowing the researchers to conduct detailed, high-quality analyses, said Eberle.
Ballantyne said the high level of preservation of trees and mosses at Ellesmere Island allowed the team to measure the ratio of oxygen isotopes in plant cellulose, providing information on water absorbed from precipitation during the Pliocene and which yielded estimates
|Contact: Ashley Ballantyne|
University of Colorado at Boulder