Snow mass decrease in the Northern Hemisphere (1979/80–2010/11)

Abstract. Snow cover has a key effect on climate change and hydrological cycling, as well as water supply to a sixth of the world's population across the Northern Hemisphere. However, reliable data on trends in snow cover in the Northern Hemisphere is lacking. Snow water equivalent (SWE) is a common measure of the amount of equivalent water of the snow pack. Here we verify the accuracy of three existing global SWE products and merge the most accurate aspects of them to generate a new SWE product covering the last 32 years (1979/80–2010/11). Using this new SWE product, we show that there has been a significant decreasing trend in the total mass of snow in the Northern Hemisphere. The most notable changes in total snow mass are −16.45 ± 6.68 and −13.55 ± 7.80 Gt year⁻¹ in January and February, respectively. These are followed by March and December, which have trends of −12.58 ± 6.88 and −10.70 ± 5.62 Gt year⁻¹, respectively, from 1979/80 to 2010/11. During the same period, the temperature in the study area raised 0.17 °C decade⁻¹, which is thought to be the main reason of SWE decline.