Long-term decline in Northern Hemispheric spring snow cover

Spring snow cover extent across the Northern Hemisphere has on average declined steadily since the 1970s and early 1980s, according to the Rutgers University Snow Lab.

Image courtesy Rutgers University Snow Lab.

Mostly due to long-term warming, snow cover is melting earlier in the season, which can have a significant impact on the length of the growing season, as well as river and reservoir levels due to reductions in spring runoff. The loss of snow cover earlier in the season can also lead to a longer wildfire season in some regions.

Spring snow cover extent in the Northern Hemisphere has been above the long-term average only four times in the last 20 years. So far this year, April was slightly above normal, but we still have to wait and see about May and June.

The number of snow-covered days during the April-June period since the early 1970s has declined at an average rate of two to three days per decade in regions such as western Canada, northern Alaska and northern Siberia. There has been little change across portions of central and eastern Canada.

The latest snow cover extent for the Northern Hemisphere shows widespread negative anomalies over northern Siberia and northern Canada.