5:15 PM - 7:15 PM
[MIS12-P08] Relationship between area change of perennial snow patch and meteorological factors for 58 years (1967-2024) in Karasawa Cirque
Keywords:Time-lapse camera, Aerial photography, Degree Days, Snow Depth, Climate change
The effects of climate change have become increasingly evident in recent years, as the highest global average temperature was recorded in 2024, following 2023, and heavy rainfall disasters are becoming more frequent in many parts of the world. Climate change is expected to have a greater impact in high latitude and high-altitude regions, and alpine ecosystems are recognized as one of the most vulnerable systems to climate change (IPCC, 2007). Japan's alpine ecosystems are in one of the world's most snowy environments. Snow provides water resources essential for human, animal and plant activities, and plays an important role as a tourism resource as well. Especially in Karasawa cirque in the southern part of the North Alps, perennial snowy valleys and beautiful autumn leaves attract many climbers. In recent years, however, snowmelt is becoming earlier and there is no snow patches left in autumn in many cases. The area change of snow patch in Karasawa was surveyed from 1967 to 1984 (Kushida et al., 1976; Kanda et al., 2015). The snow depth distribution situation in the Kamikochi area including Karasawa was precisely measured several times using aerial laser surveying (Suzuki et al., 2012, 2013; Sasaki et al., 2015). However, the long-term variation of snow patch area remains unclear due to the difficulty of continuous observation. Therefore, in this study, we analyze aerial photographs, satellite images, time-lapse camera images, and previous works, to clarify the long-term spatial and temporal changes of perennial snow patch during 1967 to 2024 in Karasawa. And furthermore, we investigated their relationship with meteorological factors.
Karasawa is one of the largest cirques in Japan with a diameter of about 2 km, surrounded by 3000-meter ridges such as Kitahotaka-dake, Okuhotaka-dake and Mae-Hotaka-dake in the southern North Alps. We used the repeat photogaraphs derived from a surveillance camera, installed at the Karasawa-koya (altitude of 2350 m) to investigate the snow and alpine ecosystems since 2007 (Oguma et al., 2019). And we collected aerial photographs taken by the Forestry Agency and Geospatial Information Authority of Japan over Karasawa in autumn every few years since 1967. We also used previous field survey maps (Kushida et al., 1979; Kanda, 2015), in addition to satellite images. The images were converted to orthographic projection, and the snow patched areas were visually detected, and their areas were measured.
As a result, the area of perennial snow patch was 104-105 m2 from the late 1960s to around 1990 varied widely from year to year. It slightly decreased from the 1990s to the early 2000s, and there were several years when there were very few snow patches left. Thereafter, the area increased again in 2006-2015, but after 2016, except for 2017, significantly decreased with many years having no or only quite a few areas of perennial snow patches.
The daily change of snowmelt area was demonstrated by image analysis of repeat photographs during 2013-2023, and the relationship with meteorological factors were investigated, with meteorological data observed by the Shinshu Mountain Environmental Research Center at Nishi-Hotakadake. The strong correlation was shown between the changes of snow area and the accumulated averaged daily temperature over 0℃ (Degree Day) during the snowmelt season. And the slope of the regression line (Degree Day factor) was correlated with the annual maximum snow depth. The Degree Day estimated from AMeDAS data near Karasawa shows statistically significant increasing trend over the past 58 years.
Further analysis is conducted using the snow depth data derived from 1km downscaling meteorological model calculations for the period 1980-2023 by the Japan Meteorological Agency's Meteorological Research Institute.
Karasawa is one of the largest cirques in Japan with a diameter of about 2 km, surrounded by 3000-meter ridges such as Kitahotaka-dake, Okuhotaka-dake and Mae-Hotaka-dake in the southern North Alps. We used the repeat photogaraphs derived from a surveillance camera, installed at the Karasawa-koya (altitude of 2350 m) to investigate the snow and alpine ecosystems since 2007 (Oguma et al., 2019). And we collected aerial photographs taken by the Forestry Agency and Geospatial Information Authority of Japan over Karasawa in autumn every few years since 1967. We also used previous field survey maps (Kushida et al., 1979; Kanda, 2015), in addition to satellite images. The images were converted to orthographic projection, and the snow patched areas were visually detected, and their areas were measured.
As a result, the area of perennial snow patch was 104-105 m2 from the late 1960s to around 1990 varied widely from year to year. It slightly decreased from the 1990s to the early 2000s, and there were several years when there were very few snow patches left. Thereafter, the area increased again in 2006-2015, but after 2016, except for 2017, significantly decreased with many years having no or only quite a few areas of perennial snow patches.
The daily change of snowmelt area was demonstrated by image analysis of repeat photographs during 2013-2023, and the relationship with meteorological factors were investigated, with meteorological data observed by the Shinshu Mountain Environmental Research Center at Nishi-Hotakadake. The strong correlation was shown between the changes of snow area and the accumulated averaged daily temperature over 0℃ (Degree Day) during the snowmelt season. And the slope of the regression line (Degree Day factor) was correlated with the annual maximum snow depth. The Degree Day estimated from AMeDAS data near Karasawa shows statistically significant increasing trend over the past 58 years.
Further analysis is conducted using the snow depth data derived from 1km downscaling meteorological model calculations for the period 1980-2023 by the Japan Meteorological Agency's Meteorological Research Institute.