Fall reaches the Canadian Arctic weeks before it touches the rest of the continent. Satellite images released by NASA this month (side-by-side comparison available) show tundra near Nunavut’s Coppermine River turning a beautiful red, orange and yellow in early September.
The images come from the Operational Land Imager aboard NASA’s Landsat 9 satellite, which photographed the same stretch of tundra, upstream of the hamlet of Kugluktuk, on July 27 and again on Sept. 6. The first shows green shrubland laced with lakes and river channels; the second shows much of that green gone, replaced by a patchwork of colour, with only pockets holding on along the water.
Autumn colour sweeps across the low-growing shrubs and tundra vegetation of Nunavut, Canada, in this image pair captured by the OLI (Operational Land Imager) on Landsat 9. Credit: NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. (CLICK TO ENLARGE)
The area is covered in willow and birch shrubs, along with blueberry and bearberry plants — low, hardy growth suited to a short Arctic summer. NASA-funded research drawing on seven years of satellite data found that colour here typically starts changing in early September and peaks by mid-month, making it one of the first places on the continent to turn each year. The display doesn’t linger: peak colour in the far north can last a week or less before the plants go dormant for winter.
The chemistry behind it is the same everywhere leaves change colour. Chlorophyll, the pigment plants use to turn sunlight into food, gives leaves their summer green. As days shorten and temperatures drop, plants stop making it, and the green fades to reveal pigments that were there all along — carotenoids, which show up yellow, and anthocyanins, which show up red.
NASA is inviting anyone interested to help track the season through its GLOBE North American Phenology Campaign. Phenology is the study of the timing of seasonal changes in nature. Volunteers record when leaves near them start turning, adding to a public database researchers use to follow fall’s spread south across the continent, a spread that, this far north, is already over almost as soon as it starts.