In a new paper, published in Nature, researchers from the Finnish Meteorological Institute (FMI) and the Environment and Climate Change Canada, working as part of European Space Agency’s (ESA’s)  Climate Change Initiative, have reliably estimated the amount of annual snow mass and changes in snow cover in the northern hemisphere between 1980 and 2018.

Warming surface temperatures are known to have driven substantial reductions in the extent and duration of northern hemisphere snow cover. Equally important, but much less well understood is snow mass—the amount of water held in the snow pack—and how it has changed over time.

The research shows that snow mass has remained the same in Eurasia and has decreased in North America, but the extent of snow cover has decreased in both regions.

This team narrowed the annual maximum snow mass for the northern hemisphere to 3062 gigatons between 1980-2018, with the peak snow mass occurring in March, a much more precise stat than previous estimates which ranged from 2500-4200 gigatons.

Overall the research team found little reduction in northern hemisphere snow mass over the four decades when looking at the annual maximum amount of snow at the turn of February-March. But  more reliable estimates enabled the team to identify different continental trends. For example, snow mass decreased by 46 gigatons per decade across North America. This was not reflected in Eurasia, but high regional variability was observed.

The study also found that in southern regions, where in winter precipitaton is more likely to fall as water rather than snow, both the extent of the snow cover and the snow mass have decreased.