Linha de permafrost diminui 130 kms em 50 anos

sexta-feira, fevereiro 19, 2010

Permafrost Line Recedes 130 Km in 50 Years, Canadian Study Finds

ScienceDaily (Feb. 17, 2010) — The southern limit of permanently frozen ground, or permafrost, is now 130 kilometers further north than it was 50 years ago in the James Bay region, according to two researchers from the Department of Biology at Université Laval.

Pictured are lichen and shrub--covered palsas surrounded by a pond resulting from melting permafrost in a bog near the village of Radisson, Canada. (Credit: Serge Payette)

In a recent issue of the scientific journal Permafrost and Periglacial Processes, Serge Payette and Simon Thibault suggest that, if the trend continues, permafrost in the region will completely disappear in the near future.

The 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.

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, the lack of long term climatic data for the area makes it impossible for the researchers to officially confirm this. 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.

Read more here/Leia mais aqui: Science Daily


Permafrost and Periglacial Processes
Volume 20 Issue 4, Pages 383 - 389

Special Issue: The Permafrost Young Researchers Network (PYRN)

Published Online: 20 Oct 2009

Copyright © 2009 John Wiley & Sons, Ltd.

Recent permafrost degradation in bogs of the James Bay area, northern Quebec, Canada

Simon Thibault, Serge Payette *
Centre d'études nordiques and Département de Biologie, Université Laval, Québec, Canada

email: Serge Payette (

*Correspondence to Serge Payette, Centre d'études nordiques and Département de Biologie, Université Laval, Québec, Canada, G1K 7P4.

Funded by:
 NSTP (Canada)


bog • permafrost • climate change • fire • palsa • peatland


Small palsas with very thin frozen layers are present within the peat deposits east of James Bay. Most of these permafrost landforms are in an advanced stage of decay within raised bogs between 51°45N and 55°N. Air photographs, air-borne surveys and ground-truthing of permafrost indicate a recent northward recession of the permafrost boundary by about 130 km, most of which likely happened in the past 50 years. Copyright © 2009 John Wiley & Sons, Ltd.

Received: 20 November 2008; Revised: 22 June 2009; Accepted: 23 June 2009


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