During the study, researchers measured the retreat of the permafrost border by observing hummocks known as "palsas," which form naturally over ice contained in the soil of northern peat bogs. Conditions in these mounds are conducive to the development of distinct vegetation—lichen, shrubs, and black spruce—that make them easy to spot in the field.
In an initial survey in 2004, the researchers examined seven bogs located between the 51st and 53rd parallels. They noted at that time that only two of the bogs contained palsas, whereas aerial photos taken in 1957 showed palsas present in all of the bogs. A second assessment in 2005 revealed that the number of palsas present in these two bogs had decreased over the course of one year by 86% and 90% respectively.
Lichen and shrubcovered palsas surrounded by a pond resulting from melting permafrost in a bog near the village of Radisson, Canada.
(Photo Credit: Serge Payette)
Helicopter flyovers between the 51st and 55th parallels also revealed that the palsas are in an advanced state of deterioration over the entire James Bay area.
While climate change is the most probable explanation for this phenomenon, there is no data available to confirm the suspicion. Professor Payette notes, however, that the average annual temperature of the northern sites he has studied for over 20 years has increased by 2 degrees Celsius. "If this trend keeps up, what is left of the palsas in the James Bay bogs will disappear altogether in the near future, and it is likely that the permafrost will suffer the same fate."
Citation: Simon Thibault, Serge Payette, 'Recent permafrost degradation in bogs of the James Bay area, northern Quebec, Canada', Permafrost and Periglacial Processes, 2009, 20 (4), 383; doi: 10.1002/ppp.660
Comments