The number of retrogressive thaw slumps - landslides caused by melting ground ice in permafrost - on Banks Island in the Canadian Arctic, increased by 60 times between 1984 and 2015. Published in Nature Communications, the paper reports the number of slumps rose from 63 in 1984 to a maximum of 4,077 in 2013. The study adds to growing evidence that cold, continuous permafrost areas can be highly sensitive to extremes of summer climate.

Retrogressive thaw slumps have become more common in the Arctic, but the timing of this recent increase and its links to climate change have not been fully established.

Antoni Lewkowicz and Robert Way used 30 years of Google Timelapse datasets and identified more than 4,000 retrogressive thaw slumps between 1984 and 2015 for the whole of Banks Island, Canada. The authors found that more than 85% of the thaw slumps occurred following four particularly warm summers (in 1998, 2010, 2011 and 2012) and about half remained active for more than three decades. Using satellite imaging, they also found that the colour of 285 lakes on the island changed from dark blue to turquoise or beige as a result of increases in the concentration of sediment in the water due to retrogressive thaw slumps.

The authors also used retrogressive thaw slump activity to estimate that 100 million tons of ice have been lost from Banks Island.