It’s July — meaning that for most of us, seeing snow on the ground would be extremely surprising. Then again, most of us don’t live in the Arctic, where considerable “snow cover” (as scientists put it) does persist into the spring and into early summer months.
In fact, climate researchers consider the amount of remaining snow cover in May and June to be a very important measurement — and this June, it was near record lows across the Northern Hemisphere, according to a new monthly analysis by researchers at Rutgers University.
It’s part of a broader climate-related trend with vast consequences for the Arctic region — which is experiencing intense wildfires across Canada and Alaska, a phenomenon probably not unrelated to this year’s dramatically low amounts of snow on the ground.
More specifically, explains Rutgers’ David Robinson, who tracks the snow record:
The June 2015 snow cover extent over North America was the second lowest on record (period of record is 49 years: 1967-2015). On average, 4,080,000 … square kilometers (2,485,000 sq. miles) of the continent was covered. This is above the 3,850,000 sq. km. in 2012, the lowest on record. The mean extent is 5,809,000 (based on the 1981-2010 period). For comparison sake, North America covers 27,709,000 sq. km. from Panama northward and including Greenland.
Eurasian snow extent and Northern Hemisphere continental extent were also both ranked second lowest for June.
To be sure, one year alone does not make a trend. But if you look at how June snow cover in the northern hemisphere has been trending of late, it’s hard to miss the punch line:
June is an important month to measure snow cover because “it’s the end of the melt season,” Robinson says. For the most part, there’s only snow left in high northern latitudes now, but how much of it there is has major climatic consequences – because less snow can mean more warming of northern latitudes.
Snow is light in color, so it reflects sunlight back to space. In contrast, darker-colored snow-free areas absorb more heat, thus raising surface temperatures — and also potentially contributing to the thawing of frozen ground beneath the surface in northern latitudes, called permafrost.
The lack of snow has had other consequences, too — including a likely contribution to currently raging wildfire seasons across northern forests. In Alaska, over 3.2 million acres has burned so far this year, a rate that puts it ahead of the all-time record year of 2004, when 6.59 million acres were ultimately consumed. Indeed, it’s already the eighth-worst wildfire year on record, and there is still plenty of time remaining. Canada, meanwhile, has seen 2,649,303.94 hectares burned so far — which converts to 6,546,562.5 acres.
How does lower snow cover exacerbate this situation? Indirectly, to be sure, but it has an influence, Robinson says.
“There’s no question that with the snow melting off earlier, you had additional days where the strongest sun of the year was able to dry out the forests, and therefore make them more susceptible to fire,” he says. Indeed, Robinson thinks that lightning strikes, which start many northern fires, may also be tied to lower snow cover.
“You’re not going to form thunderstorms over snow-covered ground very easily, you don’t get that destabilization of the atmosphere,” he says. “It’s just another example of how one thing feeds off the next.”
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