Abstract
The impacts of climate change on snowfall have received great interest in cold regions for water resources and flood risk managements. This study investigates the effects of rises in air and the sea surface temperatures, ocean currents, and sea ice on snowfall in Hokkaido, northern Japan over the period from 1961 to 2020 (60 years). Climate data observed at the 22 weather stations operated by the Japan Meteorological Agency (JMA) were analyzed. Obtained warming trends at these stations were all positive and statistically significant. Annual snowfall has increased at the 7 stations, whereas, decreased at the 2 stations. Otherwise, snowfall has neither increased nor decreased. It was found that the snowfall period has shortened mainly in the south coast. This is attributed to the fact that these sites are on the leeward side of the Eurasian monsoon and that air temperatures in the coast and the surface temperature of the Sea off Kushiro have risen sufficiently. The results suggest that the flood risk can increase in response to acceleration of the rise in a level of a river due to early melting snow in spring (March and April). Although the weather stations in the east coast are also on the leeward side, the snowfall period has not shortened. The warming trends in April are very weak in the east coast. The East Sakhalin Current come from the northern Sea of Okhotsk and melting sea ice in spring play an important role in keeping the winter period from shortening.