By Kate Ravilious
20 June 2016
(environmentalresearchweb) – Mapping high-latitude Arctic regions is a thankless task right now. Hillsides are vanishing overnight, new lakes and ponds are coming and going every week, and streams and rivers are changing course frequently. This restless landscape is due to permafrost thaw. Now a study reveals that in some regions the amount of land on the move has increased more than fourfold over the last 50 years.
Arctic warming is twice as fast as anywhere else in the world. Already average temperatures in the Arctic have risen by more than 3°C since 1900, and sea ice is melting so fast that most scientists believe we'll see an ice-free summer within the next 20 years. Permafrost, some of which has persisted for thousands of years, is rapidly turning to slush. Scars show where land has slumped, but until now few had measured how quickly this change is occurring.
Trevor Lantz and Rebecca Segal from the University of Victoria in Canada, and Steve Kokelj from the NWT Geological Survey, used aerial photos and satellite imagery to measure the impact of climate change on thaw slumping in the landscape in four ice-rich regions of northwestern Canada. Scouring the images for signs of slump activity, they were able to assess how much change there had been in the last 50 years or so.
The team found that the area impacted by slumps had increased between 2 and 407%, the average slump sizes had increased between 0.31 and 1.82ha, and slump growth rates had increased by 169 to 465 sq. m per year. Increased temperatures and precipitation have both contributed to these changes. [more]
ABSTRACT: Climate change is increasing the frequency and intensity of thermokarst, but the influences of regional climate and physiography remain poorly understood. Retrogressive thaw slumping is one of the most dynamic forms of thermokarst and affects many areas of glaciated terrain across northwestern Canada. In this study, we used air photos and satellite imagery to investigate the influence of climate and landscape factors on thaw slump dynamics. We assessed slump size, density, and growth rates in four regions of ice-rich terrain with contrasting climate and physiographic conditions: the Jesse Moraine, the Tuktoyaktuk Coastlands, the Bluenose Moraine, and the Peel Plateau. Observed increases in: (1) the area impacted by slumps (+2 to +407%), (2) average slump sizes (+0.31 to +1.82 ha), and (3) slump growth rates (+169 to +465 m2 yr−1) showed that thermokarst activity is rapidly accelerating in ice-rich morainal landscapes in the western Canadian Arctic, where slumping has become a dominant driver of geomorphic change. Differences in slump characteristics among regions indicate that slump development is strongly influenced by topography, ground ice conditions, and Quaternary history. Observed increases in slump activity occurred in conjunction with increases in air temperature and precipitation, but variation in slump activity among the four regions suggests that increased precipitation has been an important driver of change. Our observation that the most rapid intensification of slump activity occurred in the coldest environment (the Jesse Moraine on Banks Island) indicates that ice-cored landscapes in cold permafrost environments are highly vulnerable to climate change.