Earlier spring could spell trouble for permafrost
Arctic snow is fading fast. June snow cover in the Northern Hemisphere has dropped by almost 18% per decade during the past 30 years, according to a study published in Geophysical Research Letters1.
The drop in snow extent will lower the amount of sunlight reflected away from the planet — a process that has a cooling effect — by exposing darker and less reflective soil, shrubs and trees, which absorb solar radiation and re-emit the heat into the atmosphere. The change also stands to warm the permafrost, alter the timing of spring runoff into rivers and lead to earlier plant growth in spring.
“It was a bigger number than we initially thought we might have seen, but when you look at the changes in Arctic sea ice, we would expect a similarly large number,” says Chris Derksen, a cryosphere scientist at Environment Canada in Toronto and a co-author on the paper. The swift pace of the snowmelt between 1979 and 2011 exceeds the rate of decline in Arctic sea ice, which clocked in at just under 11% per decade over the same period. September 2012 saw the lowest extent of sea ice in the satellite record — and when this year’s data were included in calculations, they revealed a 13% per decade decline in sea ice and a 21.5% per decade drop in snow cover.
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