Around September or October of year, the first snow flurries make an appearance at Mount Fuji, Japan’s highest mountain. Typically, Mount Fuji is snow-capped five months out of the year.
This year, Mount Fuji got its first significant snow on September 28, 2020, 24 days earlier than in 2019 which saw the first snowfall on October 23, 2019. One news site reported a very light dusting of snow happened on September 21, 2020 but did not cover much of the mountain cap.
During years of normal snowfall, Mount Fuji is covered in snow during the winters months. This satellite image from December 29, 2013 shows a snow-capped Mount Fuji during a year with slightly higher than average snowfall.
Since then, the snow levels have been lower than normal for the 2020-2021 winter season at Mount Fuji. A snowfall towards the end of December did leave a snow cap on Mount Fuji but winds and temperatures that rose above freezing deteriorated much of it.
Satellite data that has tracked snow cover on Mount Fuji using Normalized Difference Snow Index (NDSI) observations from NASA’s Terra satellite shows that the 2020 snow levels are the lowest since 2000.
This Landsat 8 satellite image of Mount Fuji captured January 1, 2021 shows the paucity of snow covering Mount Fuji. Toshio Iguchi, a remote sensing scientist based at NASA’s Goddard Space Flight Center has calculated that through December 24, the snow cap on Mount Fuji is only 10 percent of an average year.
The low levels of snow have many Japanese citizens concerned. The snow-capped peak of Mount Fuji is normally a typical winter sight that can be seen 100km (62 miles) away in the capital city of Tokyo.
Twitter user @unananan tweeted on December 20, 2020 concerned, writing (in Japanese), “This is Mt. Fuji today … Mt. Fuji in December …? Why isn’t it snowing …! ?? Strange···········”
The lack of adequate snow cover is leaving some to worry that this is a sign of an impending eruption. Mount Fuji is an active volcano that last erupted over 300 years ago in 1707.
Mount Fuji’s Tree Line is Changing
One measurable impact on Mount Fuji’s climate is a measurable change in the mountain’s tree line. The tree line (also known as a timberline) is the altitude above which no trees can grow due to cold conditions. Hitoshi Sakio, head of the Sado Island Center for Ecological Sustainability at Niigata University, studied changes in the tree line on Mount Fuji between 1978 and 2018.
Sakio and his team found that both an increase in CO2 levels and air temperature have driven an upward change in the timberline on Mount Fuji. Carbon dioxide levels increased from 335 ppm in August 1981 to 388 ppm in 2010 and to above 400 ppm in 2015. The average maximum temperature has continued to rise during the plant growth period on Mt. Fuji with an increase of two degrees Celsius (3.6 degrees Fahrenheit).
These two increased have not only increased the biomass at the timberline but have also led to the upward advancement of Japanese Mountain Willow trees (Salix reinii) growth by 40 meters on Mount Fuji. Japanese larch trees (Larix kaempferi) have risen in altitude by about 30 meters.
Sakio, H., & Masuzawa, T. (2020). Advancing Timberline on Mt. Fuji between 1978 and 2018. Plants, 9(11), 1537. https://doi.org/10.3390/plants9111537
Voiland, A. (2021, January 12). Mount Fuji’s missing snow. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/147780/mount-fujis-missing-snow