Greening Tundra Shows Impacts of Spreading Warmth

LONDON — The Arctic is on the move. The North Pole is in the same place, but Arctic conditions have begun to shift. A study of 30 years of satellite data confirms that the difference in temperatures between the seasons has diminished.

Conditions now have shifted the equivalent of four or five degrees of latitude southward. At the same time, vegetation has moved north, colonizing the thawing permafrost.

Studies show vegetation now growing nearly 500 miles further north than it did a few decades ago.
Credit: ADialla via Climate News Network.

A team of 21 scientists from 17 institutions in seven nations reports in Nature Climate Change that as the cover of snow and ice has diminished and retreated in the Arctic Circle, the temperatures have begun to increase — at differing rates — during the four seasons. Although conditions differ from region to region, overall the growing season is beginning earlier, and the autumn freeze is starting later.

Conditions in northern latitudes now increasingly resemble those found several hundred miles further south 30 years ago. One of the authors, Bruce Forbes of the University of Lapland in Finland, told the Climate News Network that in his own research region of north-west Siberia “we are seeing more frequent and longer-lasting high pressure systems. In winter, the snow cover comes later, is deeper on average than in the 1960s, but is melting out earlier in spring.”

Climate is a complicated business, and there is always legitimate room for argument about the validity of one selected set of measurements, a potential bias in the observations, or the reliability of comparison data collected two generations earlier.

But vegetables can’t be fooled. Plants grow where they can. If deciduous shrubs are growing taller, and colonizing sites ever further north, then conditions must be getting warmer, and staying warmer.

Winners — and Losers

Professor Forbes says that indigenous reindeer herders report that alder and willow, normally stunted by the polar winter, are growing taller: his own research team has confirmed this with dendrochronology, the science of tree ring measurement.

“In a few decades, if the current trends continue, much more of the existing low shrub tundra will start to resemble woodlands as the shrubs become tree-sized”, he says.

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